Mawraw (most often used O.T. word for bitterness) does carry 'anger' as part of the definition from Strong's. I'd think, with you, such is the by-product, however. Job was clearly in 'bitterness.'
I've always associated 'bitterness' with the taste: When the Lord Jesus Christ was offered a bitter sponge, he turned away. It seems, bitterness can be thought of as synonymous with disgruntled, irritable, and complaining. We'd call such "an embittered old man/woman" for instance (angry, disgruntled, irritable).
It is often discussed in association with pessimism vs optimism. In Job's case, there was no optimism (he'd lost everything but his Deliverer), but as Nang mentioned, the Christian knows by faith there is only a positive outcome to his/her life. 1 John 3:1-3 Ephesians 2:11-22
I was a child in a very difficult family setting and often was constantly in the dredges of embittering circumstances. I believe we can, with God's indwelling, overcome our situation with blessing over cursing, but it is despite being inundated by bitter circumstance 1 John 4:4
Paul wrote from the difficulty of prison and want, unscathed by his bitter circumstance, whereby he encourages the believers to "Rejoice in the Lord" Philippians 3:1,4:4
I don't recall where I read it (Beale's
We Become What We Worship??) but it has been suggested somewhere by someone that bitterness is the result of deep-seated idolatry. Idols abound and lurk deep within the heart of man (Jeremiah 17:9!) and there are things we think we are due - that we are owed (by whomever), whether we even recognize that entitlement or not. I wonder if that is the distinction between the person who goes through horrendous circumstances without so much as a lasting complaint and the one who can't "let go" of difficulties. The one who is abused yet not bitter may not like the circumstances, but hasn't got it set in his (or her) mind what he or she deserves. Maybe what might be expected, but not what they deserve. It is, I suspect, at the root of the oft asked question - why do bad things happen to good people (as though there are really any truly good people, anyway)? What the unbeliever thinks as an obstacle to rational belief in God, is really his idol preventing him from humbling himself before The Eternal Almighty Sovereign Lord of the universe. And while that might be "expected" from those outside the camp, when it rears its ugly head within the nominal church, it should be a terrifying indication that there is something rotten that God is exposing - something of idolatry that has gone unconfessed and undealt with that will manifest itself to the world (there are a few prominent examples in view in the Western church today). And so it is that the warning we have from the writer of Hebrews might be a warning against idolatry as much as anything else. One man's idol gone unconfessed and unaddressed ultimately takes over and defiles many around him. Could there be a connection to Wormwood(??)
That little statement in Colossians reverberates around the world with echoes that resound for generations :
Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry:
For which things' sake the wrath of God cometh on the children of disobedience:
Colossians 3:5-6
Not only is coveting one of the topics of the Decalogue, not only is it found (subtextually) when Jesus elucidates on adultery and murder (or anger), but it is seen to be idolatry. Anything (no matter how good, how noble, how excellent, how beautiful and how pure) that has our affection to a degree surpassing our affection for God is an idol. We want this or that. We want more of (whatever) and how easy it is for that to be obeisance to a stealthy idol. We justify it (because it is so good, because it is a gift of God) and fail to realize that our focus on it is our undoing. God made Moses' body disappear in the wilderness. He made the ark of the covenant disappear. He had Hezekiah destroy the brazen serpent that was the point of focus for the healing of His people! And why? Because they started to follow after and worship the thing, the representation, the image more than the Giver (2 Kings 18:4). And how is that covetousness? It is a wayward heart seeking something (power, control, recognition, self-satisfaction etc...) by substituting an emblem for the actual. That emblem is powerless and only points to the reality. But when shadows - such as the feasts and the ordinances that Moses gave Israel - become greater than the reality, idolatry has set in. And we need only see how the Pharisees reacted to Jesus' words. They were blind, deaf and just plain dead to any of the reality that the Old Covenant pointed to. And while we may smugly say that our desire for another Coke bears no resemblance to the Israelite apostasy, we forget that God sees the end from the beginning. A Coke now becomes a growing appetite until we have no appetite for spiritual things because we are too busy stuffing our bellies (or eyes or ears) with things that delight us. And
if it goes too long we will, also like the Israelites, find our nostrils overflowing with the good that we overindulge in - the good that we have becomes a source of revulsion and no satisfaction at all. It becomes a source of bitterness to our souls.
But to the believer who - with Paul - has learned to be content in all situations, there is no cause for offense. Contentment and covetousness are antithetical to one another. The last several verses of Ephesians 4 (4:25-32) - which w2g already aptly pulled from all address that underlying thing that associates with bitterness (as an underlying "feeling"). Bitterness can't survive when the truth is received (v25). That truth requires that we not hold on to anger or unforgiveness or the lying accusations that often accompany intense anger (vv26-27). Honest work upholds the truth and keeps that spirit of entitlement (connected with covetousness as I think I implied in the first paragraph or two) from rising (v28). Speaking honestly and not gossiping or with a double tongue is more support for the truth (v29). If we aren't careful, we can engage in positively unholy thoughts, words and deeds that come from a bitter root - and so grieve the Spirit (v30 - this is a passing observation as grieving the Holy Spirit can be done in many ways, I suspect). And then the injunction to simply let all anger, bitterness, wrath etc be put away. And finally, forgiveness is also antithetical to bitterness (on a personal level, at least) - thus v32.
And - as you well said, Lon - a good chunk of that contentment in all situations is giving thanks always for all things (Ephesians 5:20 and cf Rom 1:21) and rejoicing in the Lord even when that doesn't (naturally speaking) make sense. Otherwise, we are letting something come between us and God. A sure sign of an idol (or seeds for one).
My apologies for the unexpected soapbox and seeming rabbit trail. But I tried to tie bitterness and idolatry together and may not have done a great job of linking them back to the discussion.