Definitions for yow
Expression of humorous surprise or emphasis.
You've been divorced four times? Yow!
Expression of pain; ouch.
Yow! I dropped it on my toe!
The New Hacker's Dictionary
[from “Zippy the Pinhead” comix] A favored hacker expression of humorous surprise or emphasis. “Yow! Check out what happens when you twiddle the foo option on this display hack!”.