A meme in which a character (usually female) censors herself in a mirror self shot by holding her finger in such a way that the finger and the reflection of the finger obscure the vulva and nipples, respectively. The meme originated with pixiv #58470507 (post #2455356), first posted in mid-August 2016.
The pose was infamously proven to be physically possible by a male anon in a thread on 4chan's /a/. Since late November 2016, the challenge had gone viral.