This is an acronym for "I've Got The App".
Mainly used on instagram in a user's description box, stating that they've got an app that will tell them you have unfollowed them, so don't even try following to unfollow.
Used to keep annoying "unfollowers" at bay; at a distance.
Sandra: I hate unfollowers
Sean: I kno right! I added this to my profile: "IGTA"
Sandra: What does that mean??
Sean: I've Got The App. Keeps stupid unfollowers who think they're "famous" away.
Sandra: Awesome! I will add it.