rudderstock

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The vertical shaft of a rudder that allows it to pivot when the tiller or steering gear is operated. Also called rudderpost.

Century Dictionary and Cyclopedia

1. n. The main piece or broadest part of the rudder, attached to the stern-post by the pintles and gudgeons.

Wiktionary

1. n. nautical The main part or blade of the rudder, which is connected by hinges, or similarly, with the sternpost of a vessel.

GNU Webster's 1913

1. n. (Naut.) The main part or blade of the rudder, which is connected by hinges, or the like, with the sternpost of a vessel.

WordNet 3.0

1. n. a vertical post at the forward edge of a rudder that enables the rudder to pivot