Definition of 'Closing Tick'
The difference between the number of stocks that closed higher than their previous trade (i.e. closed on an uptick) and the number of stocks whose closing prices were lower than their previous trade (i.e. closed on a downtick). A closing tick is used by traders as a technical indicator to denote strength or weakness in the broad market. Since buying at the close generally indicates market strength, a sustained series of positive closing ticks indicates bullishness, while a series of negative closing ticks indicates bearishness. The most widely watched closing tick is that of the New York Stock Exchange (NYSE).
Investopedia explains 'Closing Tick'
Just as the closing price of a security is of more importance to traders than its intra-day prices, the closing tick is more important than intra-day ticks because it indicates where the market closed on a given day.
For example, if the difference between stocks closing on an uptick on the NYSE and those closing on a downtick on the NYSE is 500, then the NYSE's closing tick would be 500.