A transaction/ trade that takes place at the same price level of a previous transaction/ trade, but in situation where the last recorded move was an uptick. A sell uptick order can be filled and executed only on an uptick or zero-uptick. For such orders, the trade price must always exceed the last recorded price.

It is a zero tick price in which the last recorded price is lower than the current price.

It is also known as a zero plus tick.