What does "goo" mean? A remain, perhaps?

Native speaker’s answer
Rebecca
"Goo" is used to refer to liquids that are quite sticky or slimy in nature. These liquids are usually quite viscous in nature. You can see that the green liquid in the liquid seems quite slimy, so the speaker refers to it as "goo." Other things that would be described as goo would be: slime (the kind you play with), arts and crafts liquids, and so on. Ex: Wow, this slime is so gooey and slimy! Ex: Keep adding flour into the milk until it turns into a goo.