laugh

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

• intransitive verb To express certain emotions, especially mirth or delight, by a series of spontaneous, usually unarticulated sounds often accompanied by corresponding facial and bodily movements.
• intransitive verb To show or feel amusement or good humor.
• intransitive verb To feel or express derision or contempt; mock.
• intransitive verb To feel a triumphant or exultant sense of well-being.
• intransitive verb To produce sounds resembling laughter.
• intransitive verb To affect or influence by laughter.
• intransitive verb To say with a laugh.
• noun The act of laughing.
• noun The sound of laughing; laughter.
• noun Informal Something amusing, absurd, or contemptible; a joke.
• noun Informal Fun; amusement.
• idiom (laugh all the way to the bank) To take glee in making money, especially from activity that others consider to be unimpressive or unlikely to turn a profit.
• idiom (laugh out of the other side of (one's) mouth) To see one's good fortune turn to bad; suffer a humbling reversal.
• idiom (up/in) To rejoice or exult in secret, as at another's error or defeat.

from The Century Dictionary.

• To express mirth or joy by an explosive inarticulate sound of the voice and a peculiar facial distortion; make a convulsive or chuckling noise excited by sudden merriment or pleasure.
• To be or appear gay; appear cheerful, pleasant, lively, or brilliant.
• To scoff playfully; make merry; flout; jeer: with at.
• To express laughingly; give out with jovial utterance or manner: as, he laughed his consent.
• To affect in some way by laughter, or a laughing manner; act upon by exercise of risibility: as, to laugh one's self sick or into convulsions; to laugh one out of countenance.
• noun An expression of merriment by an explosive noise; an inarticulate expression of sudden mirth or joy.
• noun Mirth or merriment, particularly at the expense of some person or thing; ridicule: used with the definite article: as, the laugh was turned against him.

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

• noun An expression of mirth peculiar to the human species; the sound heard in laughing; laughter. See laugh, v. i.
• transitive verb To affect or influence by means of laughter or ridicule.
• transitive verb To express by, or utter with, laughter; -- with out.
• transitive verb To waste in hilarity.
• transitive verb To cause to be given up on account of ridicule; as, to laugh down a reform.
• transitive verb to cause one by laughter or ridicule to abandon or give up.
• transitive verb to deride; to treat with mockery, contempt, and scorn; to despise.
• intransitive verb To show mirth, satisfaction, or derision, by peculiar movement of the muscles of the face, particularly of the mouth, causing a lighting up of the face and eyes, and usually accompanied by the emission of explosive or chuckling sounds from the chest and throat; to indulge in laughter.
• intransitive verb Fig.: To be or appear gay, cheerful, pleasant, mirthful, lively, or brilliant; to sparkle; to sport.
• intransitive verb to make an object of laughter or ridicule; to make fun of; to deride.
• intransitive verb to laugh secretly, or so as not to be observed, especially while apparently preserving a grave or serious demeanor toward the person or persons laughed at.
• intransitive verb to laugh in spite of some restraining influence; to laugh aloud.
• intransitive verb [Slang] to weep or cry; to feel regret, vexation, or disappointment after hilarity or exaltation.

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

• noun An expression of mirth particular to the human species; the sound heard in laughing; laughter.
• noun Something that provokes mirth or scorn.
• noun UK A fun person.
• verb intransitive To show mirth, satisfaction, or derision, by peculiar movement of the muscles of the face, particularly of the mouth, causing a lighting up of the face and eyes, and usually accompanied by the emission of explosive or chuckling sounds from the chest and throat; to indulge in laughter.
• verb intransitive, obsolete, figuratively To be or appear cheerful, pleasant, mirthful, lively, or brilliant; to sparkle; to sport.
• verb intransitive To make an object of laughter or ridicule; to make fun of; to deride; to mock.
• verb transitive To affect or influence by means of laughter or ridicule.
• verb transitive To express by, or utter with, laughter.

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

• noun a humorous anecdote or remark intended to provoke laughter
• noun a facial expression characteristic of a person laughing