Definition of: tenderloin

(ten′dər·loin′) noun
The tender part of the loin of beef, pork, etc., lying close to the ventral side of the lumbar vertebrae.
—the tenderloin district
1. A former district of New York City, coinciding with a certain police precinct from 23rd to 42nd streets, west of Broadway, where vice flourished and police corruption was common.
2. Hence, any district in any city which is noted for its night life, a high incidence of crime, and police leniency.