Turtleback \Tur"tle*back`\ (t[^u]r"t'l-b[a^]k`), n.
1. (Archaeol.) A rude stone celt of a form suggesting the
back of a turtle.
[Webster 1913 Suppl.]
2. (Naut.) A convex deck at the bow or stern of a vessel, so
made to shed the seas quickly.
[Webster 1913 Suppl.]