Medical Definition of BUGLEWEED. : any mint of the genus Lycopus; especially: a mildly narcotic and astringent herb (L. virginicus) of the eastern half of the United States.efinition of BUGLEWEED. 1. : any of a genus (Lycopus) of mints; especially: a North American perennial (L. virginicus) that is mildly narcotic and astringent. 2. : 1bugle. ADVERTISEMENT.