Definitions:

1. any thick, viscous matter noun
   • I got some kind of goop on my pants.
2. street names for gamma hydroxybutyrate noun
   • Gamma hydroxybutyrate, commonly referred to as GHB, is known as goop in some circles.

Synonyms:

• goo
• gook
• guck
• gunk
• muck
• ooze
• scoop
• slime
• sludge