Jizz or the act of jizzing (masturbation).

When a person uses an app on their smartphone (or iPad) to "check-in" at a business, destination, or popular point of interest. If a person checks-in, it usually lets other people know where they're at via a social media channel such as Yelp, Foursquare, Facebook, and in some cases Twitter.

Means its all good or im ayt

(verb) To directly disgrace someone with shame; an abrasive verbal attack.

Computing: When you commit some computer programming code to a code repository. Technically incorrect and a confusion of the 2 computer SVN (SubVersioN) expressions "check out" (which makes a local copy of the code for modification) and "commit" (which places code and code changes in the repository making that and all previous versions available to other users)

A coded word that brings attention to the fact that someone in the vicinity is making a move on the opposite sex (without being obvious). The move being made may be overt, subtle, physical, flirting etc. Checks are usually done to embarrass the parties involved.
Advanced users may make a more complex coding system such as check-plus, check-minus, j-check, s-check etc which may be user defined.

In chess, to threaten capture of the opposing king.