Pub'lic En'emy Num'ber One'
1. (not in official use) a criminal at the top of the FBI's list of the ten most wanted criminals.
2. a major menace to public safety, health, etc.: Cancer is Public Enemy Number One. Also,Public Enemy Number 1,Public Enemy No. 1.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.