Click here to see the NSFW pic of One Direction's Niall Horan doing what Nahum Ray calls a "squinch." What in the world does squinch mean?

Squinch

[skwench]

2015; < From Ye Olde English, perhaps variant of the obsolete squize (Old English cwȳsan) meaning "to squeeze". >

v. verb
  1. To press one's buttocks hard or together; a "buttocktion".Niall and his friend squinched their butts in a picture.
  2. To press gently.When I do Kegel exercises, I squinch my thighs.