i-adjective
harsh tasting; strongly alkaline
Describes food or drink with a sharp, bitter, or alkaline taste, often from plant compounds like tannins. Used for vegetables, tea, or wild plants.
See also: アクが強い
この山菜はアクが強いので、よく茹でてから食べてください。
These wild vegetables are harsh-tasting, so please boil them well before eating.
アクの強いお茶は苦手だ。
I don't like strongly astringent tea.
i-adjective
strong-willed; idiosyncratic; individualistic
Figurative use describing a person's personality or style as having a strong, distinctive, sometimes difficult character. Often implies a rough edge or lack of smoothness.
彼はアクの強い性格だが、憎めないところがある。
He has a strongly idiosyncratic personality, but there's something likable about him.
あの監督の映画はどれもアクが強い。
All of that director's films are fiercely individualistic.
Phrase combining アク (harshness, astringency) with 強い (strong). アク is often written in katakana; the kanji 灰汁 is used but less common. The figurative sense extends the idea of a strong, sharp taste to personality.