A frock coat
is a men's coat
introduced in the early nineteenth century characterized by knee-length skirts all around, in contrast to tail coats
. Some styles of frock coat have a seam at the waist.
Frock coats usually button only to the waist, and may be decorated with a pair of buttons a the back waist.
The term derives from frock, an ancient word for a loose outer garment, which is also the source of modern frock for a priest's robe or a woman's dress.