Green’s Dictionary of Slang

buck-wild adj.

[the state of a buck during the rutting season]

(US black) insane, crazy; extreme, intense, desperate.

[US]C. Himes ‘A Penny for Your Thoughts’ in Coll. Stories (1990) 58: It was in their buck-wild eyes, a savage gleam like cannibal fires in the jungle; in their snarling, twisted faces.
[US]C. Himes Run Man Run (1969) 7: His pale blue eyes looked buck wild. He made a terrifying picture, cursing the empty air.
Online Sl. Dict. 🌐 buck wild adj 1. uncontrollable, uncivilized; CRAZY. (‘I’m tired of going to parties where everybody is buck wild.’).
[US]Source Oct. 206: This bigass African elephant goes buckwild in the circus tent.
[US]W.J. Cobb To the Break of Dawn 108: [H]e had matured in the game from his days as a buckwild apprentice.
[US]P. Beatty Sellout (2016) 39: Oh the buckwild charge they made! / All the motherfuckin’ world wondered.

In phrases

go buck (v.) (also get buck)

(US black) to act in an outrageous, often destructive and aggressive manner.

[US]Source Oct. 190: He entertained himself by doing what the other hard-rock kids did: goin’ buck.
[US]UGK ‘Like That’ 🎵 You ever got fucked in a Maybach? / You ever got buck in the back of the ’llac?