Meaning of “den” - Learner’s Dictionary

den

noun [ C ] uk us /den/
ANIMAL'S HOME

the home of some wild animals:

a lions' den
ILLEGAL ACTIVITY

a place where secret and illegal activity happens:

a gambling den
ROOM mainly US

a room in your home where you relax, read, watch television, etc

(Definition of “den” from the Cambridge Learner’s Dictionary © Cambridge University Press)