/puy per'euh sil"in/ , n. Pharm.
a broad-spectrum semisynthetic penicillin, C 23 H 26 N 5 NaO 7 , used against certain susceptible Gram-positive and Gram-negative bacteria and certain anaerobes, esp. P. aeruginosa.
[ pipera ( zinyl ), a component of its chemical name (see PIPERAZINE, -YL) + -cillin, as in PENICILLIN ]