Webster’s Revised Unabridged Dictionary · 1913
Den
Den, n. [AS. denn; perh. akin to G. tenne floor, thrashing floor, and to AS. denu valley.] 1. A small cavern or hollow place in the side of a hill, or among rocks; esp., a cave used by a wild beast for shelter or concealment; as, a lion's den; a den of robbers.
2. A squalid place of resort; a wretched dwelling place; a haunt; as, a den of vice. "Those squalid dens, which are the reproach of great capitals." Addison.
3. Any snug or close retreat where one goes to be alone. [Colloq.]
4. [AS. denu.] A narrow glen; a ravine; a dell. [Old Eng. & Scotch] Shak.
Den, v. i. To live in, or as in, a den.
The sluggish salvages that den below. G. Fletcher.