An uptick is a transaction that occurs at a higher price than the previous trade for a given security. An uptick is sometimes called a plus tick. The opposite of an uptick is a downtick. A zero uptick, while not actually a downtick, is a trade that occurs at the same price as the prior transaction where that prior trade was an uptick. The zero uptick is sometimes called a zero-plus tick. The opposite of the zero downtick is the zero uptick.