keyway

Short definition from Wiktionary

Noun

1. 1
   A slot into which a precision attachment (a key) is fitted.
2. 2
   The whole deep way the key has to go, the hollow or cavity.
3. 3
   A guide groove.
4. 4
   The recessed part of a keyed joint, in which the key resides.
5. 5
   The groove within a modern lock that the key slides into; any lock's keyhole.