Dovetail

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.

To cut to a dovetail.

To join by means of dovetails.

To fit in or connect strongly, skillfully, or nicely; to fit ingeniously or complexly.