noun

1. A small cavern or hollow place in the side of a hill, or among rocks; especially, a cave used by a wild animal for shelter or concealment.

   “Daniel was put into the lions’ den.”

2. A squalid or wretched place; a haunt.

   “a den of vice”

3. A comfortable room not used for formal entertaining.

Synonyms: lair, family room

verb

1. To ensconce or hide oneself in (or as in) a den.