The correct spelling is shoo-in, usually with a hyphen. It has been known in that spelling and with the meaning of a certain winner from the 1930s. It came from horse racing, where a shoo-in was the winner of a rigged race.

In turn that seems to have come from the verb shoo, meaning to drive a person or an animal in a given direction by making noises or gestures

These day's the term is associated with short odd's favourites in any sport
Australia are shoo-in's for the cricket world cup
by TheDaddy April 25, 2007
to kill time talkin about nothing, or to spit game to a girl but to the point where theyre tryna do it descretely
"ya boys quit shoo shooin n lets go get this money"

"man, that nigga shoo shooin on the phone wit that hoe"
by SOP ConFident August 25, 2009
Father Mackin asked me how I liked the light show, and I was all, "Stop talkin' shoo shoo!"
by Quinn the Eskimo February 4, 2003
Shoo means, "go away, I hate you, you don't belong here, why are you still here, you're not supposed to be here, go away!". so instead of saying all that, you just say shoo!
SHOO!
what?
GO AWAY!
oh
by j00l.i.e April 26, 2003
when you want da bitch to go away
a: shoo
b: shoe?
a: just go away.
by purdygurl March 11, 2017
Exclamation of emotional empowerment.

Can be used in conjunction with -girl.
1. Shoo girl, did that shit just happen!

2. Oh my god, shoo, who the hell!

3. Thats not fair, shoo...

4. Shoo!

5. Where's my shit....shoo!

6. Shoo, I'm hungry...

7. Shoo I'm tired...

8. Shoo I'm tight...

9. Shoo I'm melancholy...
by leuqarita February 24, 2011
When you have been holding a poo in for a prolonged period and your body starts to shiver as a result
Oh no, I’ve got the shoos!
by Real Bearded Bear August 5, 2019