What is a 'sharp variation'?

I recently read a guide for players of all levels on how to improve and one of the comments was, "It's recommended to play 1.e4 as white and sharp variations as black.".

In this context, what is meant by a 'sharp variation'?  I've been playing a couple of months now and my score on chess.com generally runs just below 1100.

Thank you in advance!

It means that if you aren't careful you could cut yourself.

"ouch"

An opening where mistakes are very costly and probably losing. Most sicilians, The Slav-Botvinik and the KID are known as sharp openings.

Thank you, Chess_Enigma.

@Estragon .. Does that mean the gambit openings are considered sharp or are you referring for example to placing on bishop on b/g5 following Kc/f6?

Thanks for the clear response!  I didn't get much luck googeling the term.

Sharp variations are variations that pass through  complicated or unobvious positions where you go from what seems like an equal position to completely lost if you fail to find a good move. In a very sharp variation there are few 'so-so' moves... if it's not the right move (and there may be only one) it's a disaster.

Most gambit openings tend to be pretty sharp, or at least have plenty of sharp lines.

To me "sharp" just means a position or line where there are very few reasonable candidate moves (possibly just the one) & where a single mistake by either player can lose material and/or the game.

Many gambits are sharp: French Winawer Poisoned Pawn, Scandinavian Portuguese, Blumenfeld, Albin, Benko, etc.  Black can also sharpen the play by creating an open file to attack on, and advancing his queenside pawns as in some lines of the Sicilian Najdorf.  Another tack is to try to create a queenside pawn majority early on as in the Benoni or Semi-Slav Meran.  Sharp positions have the potential for surprising combinational blows which suddenly change the assessment of the position.  The opposite of sharp defences are solid ones where black tries to neutralize white's opening advantage while keeping his king safe and avoiding obvious positional weaknesses.  Sharp defences involve some risk as you may leave your own king vulnerable while you pursue an attack.

What about in terms of pawn structure? 

You'll find more sharp games in open games, right?  Closed structures seem to suggest positional play.

Given the definitions above, would it be fair to say non-AI chess engines (stock fish, komodo, etc.) play sharply?