Deadwood is the lower part of a ship's stem or stern.
Deadwood (Labelled "3")Starboard view of rudder, sternpost, and deadwood, showing chains that prevent dredge cable from snagging between rudder and sternpost
External links
Media related to Deadwood (ship's stern) at Wikimedia Commons
References
A Practical Course in Wooden Boat and Ship Building, page 19
Media related to Deadwood (ship's stern) at Wikimedia Commons