Bitter, sharp, harsh. Used both of taste and of character. James warns against bitter jealousy that comes from earthly, unspiritual wisdom.
James contrasts two kinds of wisdom: the wisdom from above is 'pure, peaceable, gentle,' while earthly wisdom produces 'bitter jealousy and selfish ambition' (James 3:14). The taste test of wisdom is its fruit — true wisdom produces sweetness; false wisdom leaves a bitter aftertaste of conflict and division.