How Do You Define "Humour"?

In modern English, humour (humor in US English) means being amusing or comic (possessing the ability to make people laugh) or being able to appreciate something amusing or comic ("A sense of humour.") As to what makes something amusing or comic, that varies between cultures, age groups and even individuals. A humorist is someone whose profession is making people laugh (usually through writing rather than through public speaking: the latter is usually called a comedian.) The adjective form is humorous.
The older meaning of humour is mood or temper. We still have this usage ("in a good humour.") In the MIddle Ages and even into the 18th century, it was thought that humans were governed by the "humours" or fluids in their blood, which gave them their personalities (this is where phrases like "good-humoured" come from.) It can also be a verb: "to humour someone" means to play along with their moods instead of challenging them.

The word humour comes from the Latin humor, "Moisture."

In British English (and by extension, in all the countries of the Commonwealth where English is spoken), the spelling of the word humour is h-you-m-o-you-r. It is the universal spelling of the word counsellor. In American English, the word humour is spelt without the second letter you. That is, the American spelling of the word humour is h-you-m-o-r (that is, humour).

The word humour is defined as the ability of quality of a person or a group of people or a situation or an object to invoke a feeling of amusement, entertainment or enjoyment and convey the emotion of happiness in other people. People who are humorous are said to possess a good sense of humour.

While the word humour is used in the noun form, the word humorous is used in the form of an adjective. A person who specialises in amusing people is either known as a comedian (this term is usually used in the context of a play, a film or a stage performance, that is, as a stand-up comedian) or a humorist (this term is usually used in the context of a book or an article).

For me humour is narrating or acting any incident of life or happening in life  that is normal and usual in a non-normal ( not abnormal way) un-expected and an impossible way.
  Wenish