A plus tick is a transaction which occurs at a price higher than the transaction before it, also called an uptick, but often used in relation to a zero plus tick, which is explained below.

A plus tick is an indication that the security in question is not declining at a given moment in time. In other words, the most recent traded price of a security is higher than the price it traded at prior.

The term ‘uptick’ refers to the same thing, but "plus tick" is used in reference to the first part of a zero plus tick event: an uptick occurs in which the price traded is higher than the previous price, and then a trade occurs in which the price remains the same.

The second trade is called a zero plus uptick, and indicates some stabilization at the up-ticked price. All of this applies to conversations where Uptick Rules apply to short selling.

Uptick rules were in effect for 70 years, and prevented short sellers from adding pressure to downward trends by stipulating that they could only sell securities short which had experienced an uptick at least. The rule was dissolved in 2007, but then reinstated in a new form in 2010.

What is an Uptick?
What does Ticker Mean?