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tick mark

n. A mark (often one of a series) made to show that an operation or task has been completed.

Usage examples of "tick mark".

The piece of paper had an instruction on it, and his purpose was to carry out that instruction and put a little tick mark in the adjacent box when he had carried it out.

A tick mark over the sixth digit told the dealer where to add 1 to 3 to get 4 and so complete the call.