Head"stock` (-st&obreve;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.