adverb

1) When an individual begins a romantic relationship which started on-line, and thinks that he/she has an instant, intimate connection to the other person...which just scares the shit out of the other person when there is marriage and kid talk on a first date!

2) The feeling in a nascent relationship (first date) that you're totally going to get laid that night!

3) When you meet a girl/guy for the first time and one of both of you start talking about super serious shit that happened to you as a kid when it's WAY too early
So I've got a date with this Jenn, who I met on-line, we only talked once on the phone, but emailed for like two weeks everyday and it was instamacy right away! I totally think I'm falling in-like with her, she's 5'8", nice rack, great body, and really funny...I already went to the website to figure out what our kids will look like. Would you think it was odd if someone asked you to marry them on the first date?
by The Fig February 23, 2011
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a love relationship marked by goggle-eyed infatuation, intense sexual lust, a tendency to finish each other's sentences, sleeplessness, and a certainty of failure.
"joe's going postal was an artifact of his recently-ended instamacy with jane"
by kitty thekat July 6, 2012
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