noun
1. : one of a series of bony or cartilaginous inverted arches that develop in the walls of the mouth cavity and pharynx of a vertebrate embryo and consist typically of a curved segmented bar or rod on each side meeting its fellow of the opposite side at the ventral end either directly or with the intervention of a median piece — compare branchial arch , hyoid bone , mandibular arch
2. : one of the visceral arches together with the structures surrounding and supported by it