<p><strong>Noun</strong></p><ul><li>the yellowish, acid fruit of a subtropical citrus tree, <em>Citrus limon</em>.</li><li>the tree itself.</li><li>Informal: a person or thing that proves to be defective, imperfect, or unsatisfactory; dud: His car turned out to be a lemon.</li></ul><p><strong>Adjective</strong></p><ul><li>made of or with lemon.</li><li>having the color, taste, or odor of lemon.</li></ul>