An exclamation, or expression of joy, but sometimes also sarcastic, essentially expressing the exuberance resultant from the personal realisation of
one's own great desire to "woo" or to entice others to participate in a "sex act" of some description ( or sometimes sex play,
sex theatre,
sex advertising or
sex mime ) yet also incorporating a completely imbecilic inability to be certain as to exactly _with_ _whom_.
Jimmy has five oranges, but
Betty has three apples. George has nine
bananas, and Jerry has three pears. How many fruit are there, and please don't interrupt maths classes with "woohoo".