Short for "Not sure if you saw this". Used when sending friends and family links/pics that you're not sure whether or not they've seen it. It's a sign of respect and acknowledgement that they are just as, if not more, up to date on the latest and greatest internet happenings as you are.
NSIYST *some-cool-link-to-reddit*
by Bubbler63 September 2, 2016
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