Meaning of contra-guide rudder

con'tra-guide rud"der

Pronunciation: (kon'tru-gīd"), [key]
— Naut. Naut.
  1. a rudder having a horizontal offset of its upper and lower halves to improve the flow characteristics of the propeller race.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.