noun any instruction that works first one way and then the other.
noun a hinged switch that can assume either of two positions.
— synonyms: toggle_switch, on-off_switch, on/off_switch
noun a fastener consisting of a peg or pin or crosspiece that is inserted into an eye at the end of a rope or a chain or a cable in order to fasten it to something (as another rope or chain or cable).
Examples
“Clicking a button will alternately toggle its light on OR off.”
“You can quickly toggle the case of selected text by pressing Alt+C.”