ampicillin

CIDE DICTIONARY

ampicillin, n. 

 a semisynthetic penicillin which can be considered as the common benzylpenicillin containing an amino group at the alpha benzyl position.
"It is more active against certain gram-negative bacteria than is benzylpenicillin. It found wide use in treatment of bacterial infections, and has been sold under many trade names."  [WordNet 1.5]

OXFORD DICTIONARY

ampicillin, n. Pharm. a semi-synthetic penicillin used esp. in treating infections of the urinary and respiratory tracts.

Etymology

amino + pen icillin