O-pĕr'eu-lar, a.
a. 1. (Bot.) Pertaining or belonging to the operculum.
Sense 2. (Ichth.) Pertaining or belonging to the operculum or gill-cover, which consists usually of four pieces, the anterior of which, being articulated with the head, is called the pre-opercular, while the other three, counting downward, are called the opercular, the sub-opercular, and the inter-opercular. Agassiz.