From Longman Dictionary of Contemporary Englishgillgill1 /ɡɪl/ noun [countable] 1 
HBFone of the organs on the sides of a fish through which it breathes2 → full/packed/stuffed etc to the gills
HBFone of the organs on the sides of a fish through which it breathes2 → full/packed/stuffed etc to the gillsExamples from the Corpus
gill• The bichir, in fact, not only has gills like any other fish, but a lung as well.• As well as having gills, Lungfish have primitive lungs with which they can obtain oxygen from the air.• Dab with bacterial ulcers and yellow swollen gills were found in hauls across the region.• Sediment also clogs the gills of fishes.• The first hundred yards' walking up the gill leads you into the rocky vault of Lower Ease Gill Kirk.• See their gills distend with the movement and the flurry of pectoral fins that give the subtle shunting manoeuvre.gillgill2 /dʒɪl/ noun [countable] TMa unit for measuring liquid, equal to ¼ pint. In Britain this is 0.14 litres, and in the US it is 0.12 litres.Examples from the Corpus
gill• As well as having gills, Lungfish have primitive lungs with which they can obtain oxygen from the air.• Dab with bacterial ulcers and yellow swollen gills were found in hauls across the region.• Sediment also clogs the gills of fishes.• The first hundred yards' walking up the gill leads you into the rocky vault of Lower Ease Gill Kirk.• Smith showed that water was forcibly ejected from the mouth when the gill covers were squeezed suddenly.• See their gills distend with the movement and the flurry of pectoral fins that give the subtle shunting manoeuvre. 