When someone is cute in their profile picture thumbnail, but is butt ugly when you click on it.
You: *Sees a potentially cute girl's thumbnail on Facebook* Ooh! *Click*

- Larger picture reveals that the girl has three tits and a giant zit -

You: Oh god, another Thumbnail Cute girl. *Vomit*
by TCutie August 29, 2010
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when a thumbnail pic tricks you into enlarging it and then you say no way. No s/he ain't all that.
Ooh. I thought I was gonna private message a hottie, but then I enlarged his pic and he was just thumbnail cute. Damn, guuuurl.
by bamaSeth August 30, 2015
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