To mark items on a list (with a checkmark or by crossing them out) that have been chosen for keeping or removal or that have been dealt with (for example, completed or verified as correct or satisfactory); to tick off (UK), tick (UK), cross off, strike off.
To carry out a decision recorded through the process of checking off an item on a list, including dealing with it, removing it from the possible choices, or removing the not checked items from further consideration.
To deduct union members' dues from their wages.
To clarify something by giving, or serving as, an example or a comparison.
To provide a book or other publication with pictures, diagrams or other explanatory or decorative features.