the yellowish, acid fruit of a subtropical citrus tree, Citrus limon.

the tree itself.

lemon yellow.

Informal . a person or thing that proves to be defective, imperfect, or unsatisfactory; dud

His car turned out to be a lemon.

made of or with lemon.

having the color, taste, or odor of lemon.

noun

failure , flop , junk , piece of junk , reject , bust , fiasco , loser , washout