Key

[1] A parallel-sided piece inserted into a groove cut part way into each of two parts, which prevents slippage between the two parts and they rotate together. Used to secure gears, pulleys, cranks, handles, etc.
[2] A metal instrument for turning locks and key-operated switches.
[3] An L-shaped tool for turning recessed screws (e.g., Allen key).
[4] A roughened surface which provides a basis for subsequent layers of paint or filler.
[5] To adhere to a lower layer.
[6] The act of a vandal who scratches the finish of a car with his key or other sharp instrument.
See also allen key, Allen wrench, car key, drain plug key, feather key, flat key, gib-head key, half-moon key, hexagon key, hex key, ignition key, kennedy key, nordberg key, P&W key, parallel key, Pratt and Whitney key, primary key, secondary key, square key, valve key, woodruff key.