'Headstock' definitions:

Definition of 'headstock'

noun

The stationary support in a machine or power tool that supports and drives a revolving part (as a chuck or the spindle on a lathe)

From: GCIDE

Headstock \Head"stock`\ (-st[o^]k`), n. (Mach.) A part (usually separate from the bed or frame) for supporting some of the principal working parts of a machine; as: (a) The part of a lathe that holds the revolving spindle and its attachments; -- also called poppet head, the opposite corresponding part being called a tailstock. (b) The part of a planing machine that supports the cutter, etc. [1913 Webster]