Green’s Dictionary of Slang

gook n.4

[ext. of goo n.1 (1)]

1. (US) slimy, sticky, dirty viscid matter, also distasteful food.

[US]Berrey & Van den Bark Amer. Thes. Sl.
[US]Mad mag. Jul.–Aug. n.p.: The whole pie will fall apart [...] getting icky sticky gook all over your new [...] suit.
[US]L. Bruce How to Talk Dirty 131: He [...] smeared gook on my face.
[US]H. Ellison ‘Along the Scenic Route’ in Deathbird Stories (1978) 40: The Merc sprayed JP-4 gook and water in a wide fan from its jet nozzle.
[US]S. King It (1987) 299: The gook in between the two boards will take most of the water pressure.
[US]M. Leyner Et Tu, Babe (1993) 101: I don’t want a President who wakes up with green gook in his eyes, all groggy.

2. (US) anything unpleasant; nonsense.

[US]G. Swarthout Where the Boys Are 150: I think all that gook is self-evident.
[US]F. Kohner Gidget Goes Hawaiian 63: He was full of gook, that Pete.
[US]‘Troy Conway’ Cunning Linguist (1973) 56: You mustn’t believe all that good gook about stews, anyway. Some of them can be as prim and spinsterish as a Geraldine Page movie.

In phrases

gook up (v.)

to smear such a substance on someone.

[US]R. Prather Always Leave ’Em Dying 122: If he’s to look remotely like Trammel they’ll have to gook him up with plenty of make-up, maybe fake eyebrows, a false nose, some porcelain teeth.