What does 움찔움짤 mean?

ANSWER: a flinching GIF image

움찔 means flinching, and 움짤 is an abbreviation of 움직이는 짤방, a moving 짤방. And 짤방 is Korean slang for a JPG file image,  so 움짤 literally means a moving JPG image, commonly known as an animated GIF image. That means 움찔움짤 literally means a flinching (움찔) animated GIF image (움짤).

But what is a flinching animated GIF image? 움찔움짤 may be just a longer, somewhat redundant version of 움짤, or it may be an animated GIF where only a part or parts of the image move, as suggested in the video below. Notice in the video that the only parts of the two women that are moving are essentially their mouths and arms. In other words, they are physically demonstrating what the camera's animation function does to still  photos.

DIALOG

Blue: "사진 보여줄까?"
"Shall I show you a photo?"

Pink: "그래. 머리카락을 왜 안 움직여?"
"Sure. Why don't you move your hair?"

Blue: "이거 사진이거든."
"It's a photo."

Pink: "그래도 안 움직이네."
"Anyway, it doesn't move."

Blue: "이거 사진이라고."
"I said it's a photo."

Pink: "눈도 안 깜박거리네."
"And your eyes don't blink."

Blue: "너의 사진 움직이니?
"Do your photos move?"

Pink: "응. 움직여. 볼래?
"Yeah, they move. Do you want to see?"

Blue: "뭐야? 어떻게 한 거야?
"What? How did you do that?"

Pink: "매직. 매직으로 한 거야."
"Magic. I did it with magic."

Blue: "이런 거 처음 보는데."
"I'm seeing this kind of thing for the first time."

Pink: "당연하지. 신상이니까."
"Of course. Because it's a new product."

Blue: "이름이 뭔데?"
"What's its name?"

Pink: "이름이 뭐냐하면, LG V40."
"If you're asking its name, it's LG V40."

Narrator: "신기한 영상을 손쉽게 만들어주는 매직포토."
"Magic Photo easily makes amazing images."

Pink: "사진은 움직이는 거야."
"The photos move."

Blue: "움찔, 움짤"
"Flinching, animated GIF images."