The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]WordNet (r) 3.0 (2006):
rudderpost n 1: a vertical post at the forward edge of a rudder that enables the rudder to pivot [syn: rudderpost, rudderstock]