rudderstock

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The vertical shaft of a rudder that allows it to pivot when the tiller or steering gear is operated.

from The Century Dictionary.

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

from the GNU version of the Collaborative International Dictionary of English.

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

from Wiktionary, Creative Commons Attribution/Share-Alike License.

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

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a vertical post at the forward edge of a rudder that enables the rudder to pivot