Gill
GILL, noun
1. The organ of respiration in fishes, consisting of a cartilaginous or bony arch, attached to the bones of the head, and furnished on the exterior convex side with a multitude of fleshy leaves, or fringed vascular fibrils, resembling plumes, and of a red color in a healthy state. The water is admitted by the gill-opening, and acts upon the blood as it circulates in the fibrils. Other animals also breathe by gills, as frogs in their tadpole state, lobsters, etc.
Fishes perform respiration under water by the gills.
2. The flap that hangs below the beak of a fowl.
3. The flesh under the chin.
4. In England, a pair of wheels and a frame on which timber is conveyed. [Local.]