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A fish breathes by swallowing water and passing it through gill slits on each side of its head. Blood-filled filaments on the gills extract oxygen from the water as it flows through.

gill 1

1. Zoology The respiratory organ of most aquatic animals that obtain oxygen from water, consisting of a filamentous structure of vascular membranes across which dissolved gases are exchanged.
a. often gills The wattle of a bird.
b. gills Informal The area around the chin and neck.
3. Botany One of the thin, platelike structures on the underside of the cap of a mushroom or similar fungus.
v. gilled, gill·ing, gills
1. To catch (fish) in a gill net.
2. To gut or clean (fish).
To become entangled in a gill net. Used of fish.
to the gills Informal
As full as possible; completely.

[Middle English gile, of Scandinavian origin.]

gilled adj.

gill 2

n. Abbr. gi or gi.
1. A unit of volume or capacity in the US Customary System, used in liquid measure, equal to 1/4 of a pint or four ounces (118 milliliters).
2. A unit of volume or capacity, used in dry and liquid measure, equal to 1/4 of a British Imperial pint (142 milliliters).

[Middle English gille, from Old French, wine measure, from Late Latin gillō, vessel for cooling liquids.]

gill 3

n. Chiefly British
1. A ravine.
2. A narrow stream.

[Middle English gille, from Old Norse gil.]

gill 4

also jill or Gill  (jĭl)
n. Obsolete
A girl, often one's sweetheart.

[Middle English gille, from Gille, a woman's name.]


pl n
1. (Zoology) (sometimes singular) the wattle of birds such as domestic fowl
2. green around the gills green about the gills informal looking or feeling nauseated
References in classic literature ?
Anomalous as it may seem, this is precisely the case with the whale, who systematically lives, by intervals, his full hour and more (when at the bottom) without drawing a single breath, or so much as in any way inhaling a particle of air; for, remember, he has no gills.
My heart fell down amongst my lungs and livers and things, and a hard piece of corn-crust started down my throat after it and got met on the road with a cough, and was shot across the table, and took one of the children in the eye and curled him up like a fishing-worm, and let a cry out of him the size of a warwhoop, and Tom he turned kinder blue around the gills, and it all amounted to a considerable state of things for about a quarter of a minute or as much as that, and I would a sold out for half price if there was a bidder.
asked a red-faced gentleman with a pendulous excrescence on the end of his nose, that shook like the gills of a turkey-cock.
Madam," I said, breathlessly springing forward, as a heavenly being was coldly tearing the hook from the gills of the unlucky trout, "though I am a stranger, will you do me a great favour?
O that I could see you all strung by the gills, like sardines on a twig
There the nets brought up beautiful specimens of fish: some with azure fins and tails like gold, the flesh of which is unrivalled; some nearly destitute of scales, but of exquisite flavour; others, with bony jaws, and yellow-tinged gills, as good as bonitos; all fish that would be of use to us.
Then, raising him up as Tobit raised the fish by the gills, you must pull him into the room, taking care to squeeze him so tight that he can't cry out.
They eat it raw; scales, bones, gills, and all the inside.
I have fished for trout, in Tahoe, and at a measured depth of eighty-four feet I have seen them put their noses to the bait and I could see their gills open and shut.
Nobody cares for planting the poor fungus; so she shakes down from the gills of one agaric countless spores, any one of which, being preserved, transmits new billions of spores to-morrow or next day.
The birds then collected at a short distance, yet to near that their naked necks, entirely bare of feathers, could be plainly seen, as they stretched them out with the effort of their cries, while their gristly crests, garnished with a comb and gills of deep violet, stood erect with rage.
In that supreme moment Hook did not blanch, even at the gills, but Smee and Starkey clung to each other in terror.