Definition of "ounce"

ounce¹

/aʊns/

noun
plural ounces
1. An avoirdupois ounce, weighing 1⁄16 of an avoirdupois pound, or 28.3495 grams.
2. A troy ounce, weighing 1⁄12 of a troy pound, or 480 grains, or 31.1035 grams.
3. A US fluid ounce, with a volume of 1⁄16 of a US pint, 1.8047 cubic inches or 29.5735 millilitres.
4. A British imperial fluid ounce, with a volume of 1⁄20 of an imperial pint, 1.7339 cubic inches or 28.4131 millilitres.
5. (figurative) Any small amount, a little bit.

ounce²

/aʊns/

noun
plural ounces
1. (now archaic) A large wild feline, such as a lynx or cougar.
  Quotations
  The Ounce or the vvilde Cat, is as big as a mungrell dog, this creature is by nature feirce, and more dangerous to bee met vvithall than any other creature, not fearing eyther dogge or man; […]
  1634, William Wood, “Of the Beasts that Live on the Land”, in New Englands Prospect. A True, Lively, and Experimentall Description of that Part of America, Commonly Called New England; […], London: […] Tho[mas] Cotes, for Iohn Bellamie, […], 1st part, page 23
  Halloa! another prey,The nimble Antelope!The ounce is freed; one spring,And his talons are sheath’d in her shoulders,And his teeth are red in her gore.
  1801, Robert Southey, “(please specify the page)”, in Thalaba the Destroyer, volumes (please specify |volume=I or II), London: […] [F]or T[homas] N[orton] Longman and O[wen] Rees, […], by Biggs and Cottle, […]
2. Synonym of snow leopard, Panthera uncia.
3. (cryptozoology) Synonym of onza, a particularly aggressive cougar or jaguarundi in Mexican folklore.
  Quotations
  The ounce, a leopard-like creature, is dreaded for its depredations by the Indians of Brazil.
  1911, James George Frazer, The Golden Bough, volume 8, page 235