lemon

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A spiny evergreen tree (Citrus limon) native to Asia, widely cultivated for its oval yellow fruit.
• noun The fruit of this tree, having an aromatic rind and juicy, acid pulp.
• noun Lemon yellow.
• noun Informal One that is unsatisfactory or defective.
• adjective Lemon-yellow.
• adjective Made from lemons.
• adjective Tasting or smelling like lemons.

from The Century Dictionary.

• noun The fruit of the rutaceous tree Citrus Medica, var. Limonum.
• noun The tree that yields this fruit.
• noun The borhame or sand-sole, a kind of flatfish. See lemon-sole, 1.
• noun Having lemon as a principal ingredient; impregnated or flavored with lemon: as, lemon candy.
• noun Of the color of a lemon; lemon-colored: as, lemon silk.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) An oval or roundish fruit resembling the orange, and containing a pulp usually intensely acid. It is produced by a tropical tree of the genus Citrus, the common fruit known in commerce being that of the species Citrus Limonum or Citrus Medica (var. Limonum). There are many varieties of the fruit, some of which are sweet.
• noun The tree which bears lemons; the lemon tree.
• noun (Bot.) a fragrant East Indian grass (Andropogon Shœnanthus, and perhaps other allied species), which yields the grass oil used in perfumery.
• noun (Zoöl.) a yellow European sole (Solea aurantiaca).
• noun (Chem.), [Colloq.] a white crystalline substance, inappropriately named, as it consists of an acid potassium oxalate and contains no citric acid, which is the characteristic acid of lemon; -- called also salts of sorrel. It is used in removing ink stains. See Oxalic acid, under Oxalic.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A yellowish citrus fruit.
• noun A semitropical evergreen tree, Citrus limon, that bears such fruits.
• noun A taste or flavour/flavor of lemons.
• noun A more or less bright shade of yellow associated with lemon fruits.
• noun slang A defective or inadequate item.
• noun Cockney rhyming slang Smart; cheeky, vocal.
• noun Cockney rhyming slang favour, favor.
• noun A piece of fanfiction involving explicit sex.
• adjective Containing or having the flavour/flavor and/or scent of lemons.
• adjective Of the pale yellow colour/color of lemons.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a distinctive tart flavor characteristic of lemons
• noun a small evergreen tree that originated in Asia but is widely cultivated for its fruit
• noun a strong yellow color
• noun yellow oval fruit with juicy acidic flesh
• noun an artifact (especially an automobile) that is defective or unsatisfactory