lemon

1. (uncountable, rare) Lemon juice.Examples: "[J]uſt at the laſt ſcald four or five ſpoonfuls of thick new cream, with a few drops of lemon or vinegar, muſhrooms pickled do well, […]"; "[S]tir into this, after taking from the fire, two ounces of butter cut into little bits, putting in one piece at a time, and squeeze a few drops of lemon in this sauce."; "The fact that he is drinking lemon is, therefore, an image of the bitterness of his life."rareuncountable

2. (slang) A defective or inadequate item or individual.Examples: "He didn’t realise until he’d paid for it that the car was a lemon."; "“[…]the Navy's supposed to give me a ship that goes, and a captain that fights—— That's what all this muck is for, isn't it?” “Look, it's an old story by now. We're stuck with a lemon. Misfortune of war.[…]”"Synonyms: bombcountableslanguncountable

3. (Cockney rhyming slang, shortened from “lemon flavour”) Favor.Examples: "A thousand quid for that motor? Do me a lemon! I could get it for half that."Cockneycountableslanguncountable

4. (dated, fandom slang) A piece of fanfiction involving explicit sex.Examples: "I'd really like to know what people think of this and whether I should carry on writing lemons or go and hide under a rock somewhere."; "WARNING: This story is a lemon and must be viewed with great care. If you are either under the age of 18, think graphic sex is discussing^([sic]) or you know what my writing is like you should turn away now."; "This won't be a lemon simply because I can't see myself writing anything like that."Synonyms: PWP, smutficcountabledatedslanguncountable

5. (geometry) The surface of revolution of a circular arc of angle less than 180° rotated about the straight line passing through the arc’s two endpoints.countableuncountable