Shorthand for please, but nowadays since texting shorthand isn't really used, it has actually become
something of a separate entity. It has made it into verbal speech, such as "lol", and is
pronounced "plz" or "pluz". In this context, in
in and of itself can be used to mean:
"oh please" used to call out one's bullshit.
or
"please no" a subdued beg for mercy, usually from an online roasting.