What is Longshot?
1.
When a contestant of a competition has no probability of winning, but wins anyhow, it is a longshot.
When you try to guess a result of something, but in fact you don't know at all what will be the outcome of it, that is a longshot, it is a wild guess.
I guessed the 3 last Superbowl winners, all longshots.
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2.
Contest similar to "silly swords" or "pissing contest" where two (or more) males stand behind a straight line and urinate as hard as they can. The winner of "longshot" is the one who is able to piss the farthest.
"Mike and Frank were in the back yard playing longshot. Mike won, but I think he shit his pants straining."