Definition:
'Outs' are the number of cards that will improve your poker hand.
For example, in Texas Hold'em, if you had the ace and king of clubs in the hole, and the flop came 10 of clubs, 8 of clubs, Jack of diamonds, you'd have a lot of outs: the 9 clubs that will give you the nut flush, and the 3 other queens which would give you a straight, 10 to Ace. So you'd have at least 12 'outs'.
'Outs' are the number of cards that will improve your poker hand.
For example, in Texas Hold'em, if you had the ace and king of clubs in the hole, and the flop came 10 of clubs, 8 of clubs, Jack of diamonds, you'd have a lot of outs: the 9 clubs that will give you the nut flush, and the 3 other queens which would give you a straight, 10 to Ace. So you'd have at least 12 'outs'.