The word "gill" refers to the breathing organ found in fish and other aquatic animals that allows them to extract oxygen from water. It's like a set of thin flaps or filaments that absorb oxygen and release carbon dioxide. Full definition
The trademark side gills of the Range Rover also has two alternative design schemes. (carwale.com)
Along with the BMW kidney grille, door handles and side gills in black chrome and the carbon - fiber exterior mirror caps, they accentuate the extraordinarily sporty and powerful presence of the car. (press.bmwgroup.com)
The vaquita porpoise lives in the Gulf of California, Mexico, where illegal fishing with gill nets has slashed the population by a total of 90 per cent in the past five years (newscientist.com)