Has many definitions, mainly involving taking a shit on your partner during lovemaking, hence a luvdump, or sometimes referred to when masterbationg whilst taking a crap.
MAN: Hey babe wanna try something new when we have sex later?
WOMAN:Yeah sure what are you thinking? Something kinky I hope...
MAN: Well have you heard of a 'Luvdump'?
WOMAN: Yea you dirty fuck im not letting you shit on me!!!