ˌgraməˈsīd ə n noun
( -s )
Etymology: gram -positive + -i- + -cide + -in
: a crystalline antibiotic of a polypeptide nature produced by a soil bacterium ( Bacillus brevis ) that is active against most gram-positive disease-producing bacteria in local infections but when introduced into the blood stream is destructive of red blood cells — see tyrothricin