embitter means to cause (something) to be or taste bitter; to bitter. Lexicurio rates it Rare gem — a strength score of 82 out of 100.
embitter is pronounced /ɪmˈbɪtə/.
Why “embitter” is a great word
EMBITTER — [Verb] To cause someone to feel bitter, resentful, or hostile. From the English prefix em- (a variant of en-, meaning 'to cause to be') + bitter (meaning having a sharp, acrid taste or causing pain). First recorded in use c. 1600. Unlike aggravate (which chiefly worsens a situation) or envenom (which suggests a deliberate, spiteful poisoning), embitter chronicles a slower, internal corrosion. It is the metallic aftertaste of a promise endlessly deferred, the quiet chill of a friendship turned transactional, and the gradual tarnishing of a once-bright hope—a permanent, acrid sediment of the soul, crystallized from the steady drip of disappointment.
Etymology
From em- (variant of the suffix en- with the sense ‘to become’) + bitter.
verb
- To cause (something) to be or taste bitter; to bitter.
- To cause (a positive quality such as happiness, or a thing such as an activity or one's life) to become less good or pleasurable; also, to make (a negative quality, or thing such as a disagreement) worse or more unpleasant.“He imbitters not a diſtaſtfull meſſage to a forrein Prince by his indiſcretion in delivering it.”
- To cause (someone or their feelings) to become more angry, resentful, or unfriendly; to envenom.“Sometimes it [pride] ſtirreth vp men, and imboldeneth them to offer vvrongs: ſometimes imbittereth men; and maketh them vvayvvard againſt the right: […]”