Ambiguous tag.

The male of some species is referred to as a "buck".

Species whose male is referred to as a buck:

• antelope
• deer
• dinosaur (carnivores only)
• gerbil
• goat (a more common term is "billy")
• hare (another common term is "jack")
• hamster
• kangaroo
• koala
• mouse
• rabbit (another common term is "jack")
• rat
• reindeer
• sheep (a more common term is "ram")
• squirrel
• weasel

Alternatively, you may have been looking for one of the following:

• buck_(animal_crossing) - a jock horse villager from Animal Crossing.
• buck_(blitzen) - a horse OC.
• buck_(browntailbuck) - a horse OC.
• buck_(brushfire) - a mule deer OC belonging to Brushfire.
• buck_(buckdragon) - a dragon OC.
• buck_(c0mmanderx) - a jogauni OC.
• buck_(catastrophe) - a horse OC.
• buck_(disney) - a horse who is a tertiary tritagonist from Home on the Range.
• buck_(evane) - OC belonging to a FA user named evane
• buck_(exawolf) - a dog OC.
• buck_(far_cry_3) - A.K.A. Buck Hughes. A tertiary antagonist in Far Cry 3.
• buck_(gamestop_bunny) - a (seemingly former) mascot for the GameStop chain of stores.
• buck_(ice_age) - A.K.A. Buckminster. The weasel character voiced by Simon Pegg.
• buck_(icehawk) - a caribou/reindeer OC.
• buck_(mlp) - an MLP character.
• buck_(pokémon) - The younger brother of Sinnoh Elite 4 member Flint.
• buck_(rainbow_six) - a human character from the Rainbow Six series.
• buck_(snowfyre) - an anthro Winter Sawsbuck OC
• buck_(tgd)
• buck_(tlailaxu) - an OC.
• buck_bucks - an MLP OC.
• buck_bumble_(game) - a video game released in 1998 for the N64.
• buck_bumble - the protagonist from said game.
• buck_cluck_(character) - father of the titular protagonist of Chicken Little.
• buck_hopper - a rabbit OC.
• buck_johnson - a deer OC named Buck Johnson.
• buck_naked - a character from a supermegatopia comic.
• buck_pettimore - a wolf OC.
• buck_richards - a horse OC.
• buck_sawyer - a Clydesdale horse OC.
• buck_shot - an MLP OC.
• buck_the_goat - a goat OC.
• buck_tuddrussel - a character from the Cartoon Network show Time Squad
• buck_withers_(mlp) - an MLP character (comic-only?)

Other:

• headbutt - To buck or ram one's head into someone or something.
• money - Buck is a slang term for paper money.