1) Means "Go Fuck Yourself".
Commonly used yiddish term.
2)It can also be taken literally.
It then means "go jerk off".

Mark: Hey babe, have fun last night?
Rachel: HAHA mark,you can Gai tren zich now.
Mark: Guess not.
by MysticPizza January 8, 2006
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To steal something without shame or remorse. To zich something also entails playing dumb or confused when/if confronted about the crime. Other variations include acting as if you had the right to steal the object in question or falsely claiming that the stolen goods were sold to give money to charitable causes.
Hey, did you ever get your frisbee back?

“No, I went back to the park, but it had already been ziched. There was a guy selling frisbees out of a minivan in the parking lot, so I was going to buy another one from him. Start looking thru the frisbees he had, and mine was in there. For sale! Like an hour after I left it. I was like WTF! But as soon as I started to say something, a park ranger pulled up and this dude grabs what he can, throws it in the minivan and high tails it out of the park. Weird. But man, if there’s one thing I can’t stand… it’s a zich.
by Germantown_Park&Rec August 15, 2022
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