look up any word, like hipster:
 
1.
When someone you have just met friends or messages you on facebook via smartphone during the time it took you to leave the bar and get home.
"Holy sh*t, she instastalked me. I can't decide if that's cool or not."

Or

"Don't friend her yet, your too close to instastalk territory."
by Drewsmits February 09, 2010
 
2.
verb:
To stalk someone on Instagram.

This is a development from the traditional Facebook stalk, as there are many more users that will allow their Instagram account to be public, and therefore open to Instastalkers (noun).
I know she goes to the gym, because I instastalked her.

I've made my Instagram account public, so everyone can instastalk me.
by Buggiful January 30, 2014