Short for saltine crackwhore. A play on the words saltine crackER. A decreet way to describe a girl as a crackwhore to a friend while near her without her knowing what you mean. Also can be used in plurel to describe a group of crackwhores. Saltines.
You and a friend are in line at the movies and a girl you think looks like a crackwhore is in line in front of you. You simply look to your friend and ask "Saltine?". If he agrees he simply replies in a agreeing tone "Saltine!".
She has no idea what was even said about her. She might offer you a cracker though if she has some thinking you are hungry.