The loop your face makes when you’re listening but not very interested, I.E., An eye roll, nod, deep sigh, or nom-sincere smile. Sometimes unintentional, but can be done deliberately for effect.
Usually under two seconds long, and usually sarcastic or born out of sheer boredom and a desire to be polite when you’d rather be anywhere else. Also used as profile pictures on popular internet sites.
(At a dinner party, trying to tell a story)
*The person adjacent to you, nodding and smiling over and over again*
“I was trying to tell you about this, but you’re just using a resting gif-face with me”
Alternatively, “Yeah, I don’t really care about their story, so I blanked and used my resting gif-face.
Or, “Man I rewatched that video I was in, I totally had a resting gif-face”