O-mouthed - You’re so dumbfounded you look like a goat that just saw a f

You’re so dumbfounded you look like a goat that just saw a flamingo do the cha-cha.

I found out my crush was dating my best friend. I was O-mouthed.

My dog ate my homework and got an A. I was O-mouthed.

I saw my mom's ex at the grocery store. I was O-mouthed.