Its typically a Limit term meaning to call more than 1 bet in 1 go e.g.
Player 1 bets, player 2 raises (to 2 bets) , You Cold call the 2 bets.
It can be used in No Limit meaning pretty much the same thing, but bet sizes are less defined so
Player 1 raises to 6BB, You cold call with 66 hoping to hit your set.
Welcome to FTR
Edit: The reasoning behind that Sklansky quote is that if your hand is strong enough to cold call with, then you should almost always be raising instead.