oxacillin UK /ˌɒk.səˈsɪl.ɪn/US /ˌɑk.səˈsɪl.ɪn/ noun1 •A narrow-spectrum beta-lactam antibiotic made by chemical modification of penicillin and administered in the form of its hydrated sodium salt C₁₉H₁₈N₃NaO₅S·H₂O to treat infections caused by penicillin-resistant staphylococci. formsoxacillins
