According to Seinfeld episode 908 (The Betrayal), an unvitation (sometimes spelled un-vitation) is when you send someone an invitation to an event knowing that the person will not attend. Unvitation are usually sent for events in which the invitees give gifts to the inviter (a birthday or wedding for example). The hope is that the people who can’t attend will feel guilty and respond by sending nicer presents.
Billy: How come you get better birthday gifts from your Grandmother then I do?
Bobby: Because my Grandmother lives 3,000 miles away and I always send her an unvitation to my birthday party.
by bosssman September 2, 2006
According to Seinfeld episode 908 (The Betrayal), an unvitation (sometimes spelled un-vitation) is when you send someone an invitation to an event knowing that the person will not attend. Unvitation are usually sent for events in which the invitees give gifts to the inviter (a birthday or wedding for example). The hope is that the people who can’t attend will feel guilty and respond by sending nicer presents.
Billy: How come you get better birthday gifts from your Grandmother then I do?
Bobby: Because my Grandmother lives 3,000 miles away and I always send her an unvitation to my birthday party.
by bosssman September 1, 2006
noun: An invitation to something where the inviter already knows there's no way the invited can possibly make it. That way he still gets credit for pretending to want to hang out with them.

verb: The act of inviting a person to an event, knowing full well that that can't make it, when you didn't really want them to go anyways.
noun: "Yea, I got the 'unvite' again from Shane. He knows I can't possibly go to Halloween Horror Nights this weekend, what a douche. Then he acts all upset that I can't make it. He's such an ass."

verb: "Philip has to study for a final tonight, so he can't go. Prolly I'll unvite him anyways. That way I still get credit for asking him to hang out"
by Bonnie Brown Eyes September 30, 2009
Sending an invitation very last minute with the hope invitee will already have plans. Unvites are used when you do not want someone to attend but NOT sending them an invitation would be rude.
An Unvite will say something like this:
"Sorry such short notice; I'll understand if you can't make it."
by MystinaJ February 13, 2009
An unvitation can take a few different forms, most notably;

1. Original.
Seinfeld episode "The Betrayal"
A last minute invitation to an event such as a wedding, birthday, or other gift giving gathering. An unvitation is sent to someone who the sender does not want to be present at the gathering, and with the last minute notification they would be unable to attend. The desired result is that the recipient will feel obligated to buy the sender a gift, because they received an invitation, yet the sender does not ever need to host this person.

2. "You were invited"
A last minute invitation to an event that had been planned for a longer period of time. The recipient of this unvitation often would have been able to attend the event had they been included in the planning process, but by the time they are made aware of the plans, they can not. The sender often uses this unvitation to deflect guilt by saying "But you were invited."

3. Hollow empathy.
An invitation to a social gathering that is already underway. Often the sender of this unvitation is seeking to appear empathetic by inviting a lower status friend who had been excluded. Meanwhile, it is common that the sender knows the recipient is most likely waiting, and hoping for the invite. The sender knows that they could have extended the invitation earlier, but by waiting they received the status bump of being the recipient's ticket to the gathering. The sender can signal their virtue by having offered the invitation.
Dave "Hey you guys didn't invite me hunting all season, what's up with that?"

Cory " I did invite you but you didn't come"

Dave " You had it planned for weeks but call me the night before at 9pm, that's an unvitation"

Wife " I guess we should send them a gift, they did invite us after all."

Husband " That was an unvitation, they know we can't get last minute child care. They just want more gifts."

Christine " Aww why isn't Becky here?" *ring ring* " Aww Becky you should come join us here."

Becky " No thanks, you could have invited me earlier, I'm not just sitting around waiting for an unvitation!"
by D Masterson November 21, 2019
To un-invite somebody. After you have given an invitation you change your mind and go ahead and un-invite them. Ref: from the Seinfeld episode
I got an unvite. I've just been unvited!
by Lindsay November 26, 2003
When you see somebody you haven't seen in awhile, and you invite them to your abode with the expectation that they will not come over.
"Hey so did you get invited to Brianna's party tonight?"

"Yeah did you?"

Yeah...did Devin?"

"Kinda...he found out through us, so though pity she unvited him."
by John Johnski May 15, 2010