Definition of phenobarb in US English:

phenobarb

(also phenobarb.)

noun

informal
  • Phenobarbital.

Origin

1950s; earliest use found in William Styron (1925–2006), novelist. Shortened from either phenobarbital or phenobarbitone.

Pronunciation

phenobarb

/ˌfiːnəʊˈbɑːb/