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 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 deduct union members' dues from their wages.
To select (something or someone) for a specific purpose.
To distinguish, make obvious the distinction between (two things) or of (something).
Used other than figuratively or idiomatically: to separate or isolate.