gak /ɡak, ɡæk 
/ (also gack) informal ▸ noun 2 a sticky or messy substance: the shower failed to remove the gak from my hair.
▸ exclamation used to express distaste or disgust: Gak! There she is again!
– ORIGIN 1970s : imitative; the form gak dates from the 1990s .
EnglishOxford New American Dictionary
