To fit (a lock) with a key.
To fit (pieces of a mechanical assembly) with a key to maintain the orientation between them.
To mark or indicate with a symbol indicating membership in a class.
(telegraphy and radio telegraphy) To depress (a telegraph key).
To operate (the transmitter switch of a two-way radio).
(more usually to key in) To enter (information) by typing on a keyboard or keypad.
Our instructor told us to key in our user IDs.
To vandalize (a car, etc.) by scratching with an implement such as a key.
He keyed the car that had taken his parking spot.
To link (as one might do with a key or legend).
To be identified as a certain taxon when using a key.
To modify (an advertisement) so as to target a particular group or demographic.
To attune to; to set at; to pitch.
To fasten or secure firmly; to fasten or tighten with keys or wedges.