Gill meaning : (animal anatomy) a breathing organ of fish and other aquatic animals (of a fish) a gill slit or gill cover One of the radial folds on the underside of the cap of a mushroom, on the surface of which the spore-producing organs are borne (animal anatomy) the fleshy flap that hangs below the beak of a fowl; a wattle The flesh under or about the chin; a wattle (spinning) one of the combs of closely ranged steel pins which divide the ribbons of flax fiber or wool into fewer parallel filaments To remove the gills from a fish as part of gutting and cleaning it To catch (a fish) in a gillnet To be or become entangled in a gillnet