An insincere invitation, made by someone who does not actually intend to follow through with a genuine invitation.
Person A: "Hey! Let's get together sometime and go bowling!"
Person B, sensing an invitease: "Yea...that would be really swell...what's a good day for you?"
Person A (pretending not to hear): "Cool! See ya!"
A gravity invite is when someone is so excited to invite someone to their party, shin-dig or box-social, that they invite everyone/anything within their vicinity. They may also invite anyone that is associated with that person.
Craig: Hey Greg! You should totally come to my party, its gonna be super-stylin! Hey Jenny you should come too and bring the guy in that yellow shirt..
Jenny: Thats Paul the rapist....
Craig: Greg do you know Paul?
Greg: He once butt fucked me without consent...
Craig: Awesome, he is invited
Paul: Cool... I will bring my butt fucking gear. Thank god for gravity invites