noun
A decorative knot with two loops, resembling a butterfly. Used for shoelaces, ribbons, and gift wrapping.
靴ひもを蝶結びにしてください。
Please tie your shoelaces in a bow.
プレゼントにリボンを蝶結びにした。
I tied the ribbon on the present into a bow.
リボン結び is a more general term for ribbon knots, while 蝶結び specifically refers to the butterfly-shaped bow with two loops.
Compound of 蝶 (butterfly) and 結び (knot), from the resemblance of the two loops to butterfly wings.