Something/someone you wouldn't expect to win but they could. The first defitinition on UD is correct, but the term can also be used to refer to sports teams.
Basically in reference to, lets say Ohio State in the 2010 NCAA March Madness Bracket challenge. Most people are not expecting Ohio State to win or be in the final four, but it's posibly they could pop up and win, or at the least make a finalfour appearance.
George predicted 4 teams he thought would be in the final four, but also figured that Ohio State would be the darkhorse of the 2010 Brackets if there was one.
"I think Kansas, Syracuse, Kentucky and Duke will be in the final four, and if there is a darkhorse I think it could be Ohio State"
Darkhorse is a person who everyone expects to be last in a race.
Think of it this way. The person who looks like he can never get laid defies the odds and gets any girl he can by being sly,shy and cunning. Although he's not a player, he can really charm the ladies.
Lady: Hello! How are you?
Darkhorse: Good, yea. Haha. Where're you from?
Lady: Oh. Just take me now baby.
did you see that guy! I never thought such a nerdy looking boy could get that chick! That guy is definately a darkhorse.
anything mysterious, dangerous, unusual, unexpected, confusing, or sketchy
synonomus with "sketchy"
when you see a man walking around at midnight, you might say that he is a darkhorse, or that the situation is darkhorse because that is an unusual event
basically this word can be used in any form
ex. "that guy is a major darkhorse" (that guy is mysterious)
ex. "that game was so darkhorse" (that game was confusing)
ex. "darkhorse!" (exclaiming that something is sketchy)
v. the act of engaging in sexual acts with some one who has passed out.
n. a person who darkhorses
"I heard Julie and Marvin had sex last night."
"Actually, Julie was darkhorsed."
The origins of 'darkhorse' are somewhat vague but modern scholars agree it was originally an Essex term.
In it's simplest form it means "to have bum sex"
It is usually abbreviated to "horsey"
I'm just going out to feed the horsey
I can't sit down, I've been riding the darkhorse.
Fancy some horsey?
My dod Charles you are walking oddly tonight. Horsey?