Particularly pungent, temporary quarters for the homeless lined with stray dog fur, feces, and syringes. Often found over heated vents in winter or under bridges in the rainy season.
Damn son, you smells like a bum nest.
Where homeless people sleep, drink tall boys, and proceed in crack induced homo-sexual activities (ass fucking, blow jobs, etc etc). Bum Nests can be found in large metro areas, and typically smell like shit, and have used cardboard signs with "God Bless" scribbled on them. Also BumNest is a new and upcoming magazine out of the Northwest.
Drunken Frat Boy: "Heh guys, I went to go piss over in the alley, but I had to step over a goddamn bum in his bum nest."