Source : Webster's Revised Unabridged Dictionary (1913)

Rudderpost \Rud"der*post\, n. (Naut.)
   The shank of a rudder, having the blade at one end and the
   attachments for operating it at the other.

Source : WordNet®

rudderpost
     n : a vertical post at the forward edge of a rudder that enables
         the rudder to pivot [syn: {rudderstock}]