Iterjection. (1) An exclamation of surprise or 2) a synonym for sighing. Example: (1) Gyah! I can't believe I have a 10 page paper due tomorrow! (2) Gyah. I just don't feel like doing the laundry right now.
GYAH
Meaning of GYAH in English
Slang English vocab. Английский сленговый словарь. 2012