(n): any weight unit used in pharmacy; an ounce is equal to 480 grains and a pound is equal to 12 ounces
(n): any of the unit of the troy system of weights
(n): a unit of weight equal to one sixteenth of a pound or 16 drams or 28.349 grams
(n): any of the units of the avoirdupois system of weights
(n): large feline of upland central Asia having long thick whitish fur
(n): any of several large cats typically able to roar and living in the wild
The OED marks its general 'medium-sized member of the cat family' definition as archaic, but not the specific definition 'the snow leopard, Panthera uncia'.
Apparently this sense of 'ounce' appears in ounce stone, which is 'a precious stone mentioned by Pliny, now understood to have been amber'.
See the last two WeirdNet definitions. I had no idea this word described a type of wild cat.