Definitions of humour:

noun: the trait of appreciating (and being able to express) the humorous
noun: the quality of being funny
noun: (Middle Ages) one of the four fluids in the body whose balance was believed to determine your emotional and physical state
noun: a message whose ingenuity or verbal skill or incongruity has the power to evoke laughter
noun: a characteristic (habitual or relatively temporary) state of feeling
noun: the liquid parts of the body
verb: put into a good mood