Nosh

Pronounced with a long 'O' like nose.
This is a form of g-slang when a person wants to say, "No $h!t" but needs to keep their vocabulary clean.

Dave: "Can you believe I bought these shoes for three dollars?!"
Sweets: "Nosh?!!"

g-slang

Profanity that has been altered and deemed acceptable for public use.

Some examples of 'g-slang' where common profanity has been replaced by acceptable words or phrases:
"I just smashed my hand in that 'Freaking' door!"
"Son of a 'Bee Sting!'"
"Holy 'Shiit'ake mushrooms!"