Exclamation which serves to justify a stupid and unwitty joke, which is normally made intentionally.
Etymology - Literally a slurred and quick "get it?" was first introduced in the late 90s by a sicilian/englishman named E.Zimmatore.
The diffusion of the word was quick and vast, mainly dominant within south east England, from London to Brighton and in certain areas of Paris.
Ed's cat got run over and died;
John asks Ed:
"How's your cat? Geedit!"