Dovetail (?), n. (Carp.) A flaring tenon, or tongue (shaped like a bird's tail spread), and a mortise, or socket, into which it fits tightly, making an interlocking joint between two pieces which resists pulling a part in all directions except one.
[1913 Webster]

Dovetail molding (Arch.), a molding of any convex section arranged in a sort of zigzag, like a series of dovetails. -- Dovetail saw (Carp.), a saw used in dovetailing.
[1913 Webster]