n. - 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.
n. - A squalid place of resort; a wretched dwelling place; a haunt; as, a den of vice.
n. - Any snug or close retreat where one goes to be alone.
n. - A narrow glen; a ravine; a dell.
v. i. - To live in, or as in, a den.