secobarbital n barbiturate that is a white odorless slightly bitter powder (trade name Seconal) used as a sodium salt for sedation and to treat convulsions Usage(s) Half an hour before it ends, the doctors give an antagonist drug (usually secobarbital or chlorpromazine) to cut short LSD's lingering effects; they make sure that the patient . Synonym(s) secobarbital sodium Seconal red devil