Dizz is an abbreviation. It really is short for "dirty jizz" or semen that has been contaminated by dirt or unclean particles. It is not to be mistaken for dizzy which means something else altogether.
"Oh no, there is semen in that dirt pile!"
"It is no longer just semen; it is dizz!!!!"
You're just walking down the corridor and then you see your friends! So you go up to them and you shout as loud as you can "What's the dizz!?"
Or
Your just walking down the hallway and then some guy runs into you, so you turn around, push them and say "Dude! What's your dizz?!"