gill

Definition

n. the part of a fish's body that it uses to breathe underwater. It takes oxygen out of the water and lets the fish live without air.

n. the respiratory organ of aquatic animals, such as fish and amphibians, that extracts dissolved oxygen from water. Typically located on the sides of the head and protected by a bony cover.

simple

“The fish moved its gills to breathe in the tank.”

contextual

“As the shark swims forward, water passes over its gills to provide the oxygen needed for its muscles.”

complex

“Unlike mammals that rely on lungs, most teleost fish utilize a counter-current exchange system within their gills to maximize the efficiency of gas exchange from the surrounding water.”

Usually used in the plural ('gills') when referring to the respiratory system as a whole.

“Scientists from ZMT and ICBM took a closer look at the microorganisms living in the gills of coral reef fish.”

Phys.org 27 Sept 2026

* As an English surname, converged from variants of Giles (sometimes through Dutch), Julian, and William. * As a northern English surname, from Middle English gil (“ravine, glen”), from Old Norse gil. The Old Norse is also a source of the Norwegian surname. * As an Irish and Scottish Gaelic surname, variant of McGill. * Also as an Irish surname, variant of Gall. * As a Jewish/Israeli given name, as well as surname, from Hebrew גיל (“joy”). * As a German surname, variant of Gilger. * As a Sikh Punjabi surname originating in India, from ਗਿੱਲ (gill, “moisture”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.