1. A wooden peg or pin inserted into the eye at the end of rope in order to fasten it to something.
2. Any instruction that works first one way and then the other; it turns something on the first time it is used and then turns it off the next time.

1. To fasten with, or as if with, a toggle.
2. To provide with a toggle or toggles.
3. To release by a toggle switch, of a bomb from an airplane.

An electronic device with two states or a program option that can be turned on or off using the same action, such as a mouse click.
In computing, to switch between two settings. In software a toggle is usually triggered by the same code, so it is important that this code only has two meanings. An example is the use of the same character in a text file to indicate both opening and closing quotation marks; if the same character is also used to mean an apostrophe, then conversion, via a toggle switch, for a desktop publishing system that uses different opening and closing quotation marks, will not be carried out correctly.

To switch back and forth between two states. For example, the Num Lock key on an IBM-style keyboard toggles the numeric keypad between numbers and cursor movement.