Definition

RBF (Resting Bitch Face): a neutral facial expression that unintentionally looks annoyed, unfriendly, or unapproachable.

Examples

"Sorry if I looked annoyed during the meeting—that’s just my RBF."

"He’s super friendly, but his RBF makes people think he’s upset."

"My RBF scares off strangers even when I’m in a great mood."