1. A lid-like or flap-like anatomical structure that covers or closes an opening, especially in fish and mollusks.
Usage: plural of operculum; biology/zoology term; commonly refers to the gill cover in fish

Examples

• Fish use their operculums to protect their gills from damage.
• The operculums of different fish species vary greatly in shape and size.
• When the fish opens its mouth, the operculums flare outward to increase water flow.
• Marine biologists examined the operculums to identify the species.
• The operculums close tightly when the fish is resting.