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.-fig.: to be or appear gay, cheerful, pleasant, mirthful, lively, or brilliant; to sparkle; to sport.-to affect or influence by means of laughter or ridicule.-to express by, or utter with, laughter; -- with out.-an expression of mirth peculiar to the human species; the sound heard in laughing; laughter. see laugh, v. i.