swal·low·tail / ˈswälōˌtāl/ • n. (also swallowtail butterfly) a large brightly colored butterfly (family Papilionidae) with taillike projections (suggestive of a swallow’s tail) on the hind wings. Many genera and species include the eastern tiger swallowtail (Papilio glaucus) of eastern North America.

swallowtail.
1. Dovetail moulding or triangular fret moulding consisting of a series of adjacent equilateral triangles, each set alternately with apex and base uppermost, the series framed by a system of fillets joining at acute angles, and decorating a band.

2. Guelphic crenellation. See battlement.