check

Check (n.) -- a call to action requesting other people to show/display something that you also have

Sentence format: "(noun) the thing you want to show off check"

In 2019/2020 this is trending on bite-sized user-generated-video sharing platforms.

Etymology:

Coin check (military) refers to a challenge coin. If somebody from the U.S. military receives a challenge coin (an honor) they can be socially expected to carry it at all times. So at the bar, somebody can call out "coin check" and anybody that does not have their coin will buy a round. These checks got popular in the 2000s.

WTF:

I have no idea how this word usage transplanted from military dudes to teenage girls.

"80s hair check"

You would say this on TikTok if you are sharing a clip with you having 80s hair. This is an invitation for other people with 80s hair to reply and show off their hair.