gill arch

1. One of several bony or cartilaginous arches located on either side of the pharynx and supporting the gills in fish and amphibians.
2. Embryology. One of several corresponding arches in the embryo of a higher vertebrate that develop into structures of the ear and neck.

The noun has one meaning:

Meaning #1: one of the bony or cartilaginous arches on each side of the pharynx that support the gills of fishes and aquatic amphibians
  Synonyms: branchial arch, gill bar