anything. absolutely anything, be it good, bad, or neither. shit altogether replaces the words: stuff, things, and other such placeholders. SHIT is the ultimate sentence filler, capible of carrying great importance or complete uselessness.
'I heard some shit about her yesterday....yeah apparently she's a whore.'
'He's been involved with so much shit lately.....I mean, he just signed a record deal!!'
'Help me carry this shit, my waterbottle's in it and it's wicked heavy.'