Refers to the taste that remains in the mouth after eating or drinking. Also used figuratively for the lingering feeling or impression after an experience.
This coffee has a clean aftertaste.
The fight with him left a bad aftertaste.
His words left a bitter aftertaste.
This drama had an ending that left a good aftertaste.
That ramen leaves an aftertaste in your mouth.
Compound of 後 (あと, 'after') and 味 (あじ, 'taste').