sourest
adjective
Definitions
Having an acidic, sharp or tangy taste.
Example: Lemons have a sour taste.
Made rancid by fermentation, etc.
Example: Don't drink that milk; it's turned sour.
Tasting or smelling rancid.
Example: His sour breath makes it unpleasing to talk to him.
(of a person's character) Peevish or bad-tempered.
Example: He gave me a sour look.