Means, to be ignored or overlooked, not paid their respect (or disrespect) when an effort is made by a person or group of persons. Usualy refers to underground hip hop but not always.
'It ain't right that Nas always be slept on by today's radio and tv stations' =
by Adrian October 10, 2006
overlooked; forgotten, ignored.
"He slept on the cd so i scooped that shit up."
by iq December 02, 2002