antibiotic

an·ti·bi·ot·ic

antibiotic

n.
  1. A chemical substance derived from a mold or bacterium that kills microorganisms and cures infections.
  2. any chemical substance having therapeutically useful antibacterial or antifungal activity; -- used commonly but loosely for synthetic as well as natural antimicrobial agents.

antibiotic

adj.
  1. of or pertaining to an antibiotic.
  2. having antimicrobial activity; capable of killing microbes.