| PEN | an intruder who passes into or through (often by overcoming resistance) |
|---|---|
| PEN | type genus of the family Peneidae |
| PEN | a Dravidian language spoken in south central India |
| PEN | formerly the basic unit of money in Hungary until it was replaced by the forint in 1946 |
| PEN | short-legged flightless birds of cold southern especially Antarctic regions having webbed feet and wings modified as flippers |
| PEN | of or relating to the penis |
| PEN | a drug (trade name Cuprimine) used to treat heavy metal poisoning and Wilson's disease and severe arthritis |
| PEN | any of various antibiotics obtained from penicillium molds (or produced synthetically) and used in the treatment of various infections and diseases |
| PEN | the first form of penicillin that was isolated in Great Britain |
| PEN | the penicillin that constitutes the principal component of many commercial antibiotics |
| PEN | a penicillin that is similar in antibiotic action to penicillin G but is obtained differently |
| PEN | a crystalline penicillin similar in action to penicillin G but more resistant to the action of gastric acids |