I can't speak Engrish

Me: Ooh, can I sit in on your English class?!

KH: Haha, sure... wait, how do you say that in English?

Me: Um... you know... "sit in on a class..."

KH: Isn't there a specific word for it?

Me: Yeah, there is... it's at the tip of my tongue... 

KH: Uh-huh...

Me: I'm losing my English!

KH: Hahaha.

Me: Give me one second.

KH: Your second's up!

Me: Wait, I swear I know this!

***frantically IMs Dave/Oliver in Boston***

Me: I got it! It's called "AUDITING!"

청강하다 = to audit a course/sit in on a lecture