A sliding part of some mechanism; a device which slides or may be slid; New Zealand, a serving hatch (see sense j); Music, on wind instruments…

A thing or part which slides or may be slid; esp. a sliding part or device in some mechanical apparatus.

A device or part of mechanism that moves along a support; esp. one used to convey something from one end of the support to the other.

A sliding motion or action; a mechanism (esp. on a firearm) which delivers such a motion or action.

a ‘block’ or piece of metal which slides between or upon guides or guide-bars.

Mechanics. A part that is capable of sliding in the direction of its length.