noun

• (US) An uncastrated sheep, a ram.
• (Africa) An antelope of either sex; compare with Afrikaans bok.
  "There are all kinds of game in the valley, and you are unlucky if you do not see a giraffe or an ostrich, or at least a herd of buck."
• (British, obsolete) A fop or dandy.
  "This pusillanimous creature thinks himself, and would be thought, a buck."
• (US, dated, derogatory) A black or Native American man.
  "But this buck claimed he was a big war chief with the Nawyecky Comanches."

verb

• (intransitive) To copulate, as bucks and does.

verb

• (intransitive) To bend; buckle.
• (intransitive, of a horse or similar saddle or pack animal) To leap upward arching its back, coming down with head low and forelegs stiff, forcefully kicking its hind legs upward, often in an attempt to dislodge or throw a rider or pack.
  "1849, Jackey Jackey, The Statement of the Aboriginal Native Jackey Jackey, who Accompanied Mr. Kennedy, William Carron, Narrative of an Expedition Undertaken Under the Direction of the Late Mr. Assistant Surveyor E. B. Kennedy, 2004 Gutenberg Australia eBook #0201121, At the same time we got speared, the horses got speared too, and jumped and bucked all about, and got into the swamp."
• (transitive, of a horse or similar saddle or pack animal) To throw (a rider or pack) by bucking.
  "The brute that he was riding had nearly bucked him out of the saddle."
• (intransitive, by extension) To resist obstinately; oppose or object strongly.
  "The vice president bucked at the board’s latest solution."

noun

• (Scotland) The beech tree.
  "There is in it also woodes of buck, and deir in them."