thumbnailed 

When someone looks good in a thumbnail picture, and you click on it only to find out they don't look nearly as good in the full picture, you've just been thumbnailed.

"Ooh, she looks hot."
*click*
"Dammit! Thumbnailed again!"

thumbnailed by ibbit June 28, 2009

Thumbnailed 

That feeling in your stomach that you get after looking at a hot girl's thumbnail on Facebook, clicking on it, and realizing that she's ugly as shit.

Person 1: Bro, she looks so hot. Click on her picture.
Person 2: LOL ALRIGHT
Person 1: DAMN, This computer is super slow.

Person 2: SHUT UP DOOD LOL
Person 1: AHHH WTF SHE'S UGLY AS SHIT
Person 2: HAHAHA HOW DOES YOUR ASS FEEL? YOU JUST GOT THUMBNAILED.

Thumbnailed by Godlinessicity July 6, 2011

Thumbnail 

The cover photo for a YouTube video. Usually to get your attention or show what the video is about.

Put boobs in the thumbnail to get more views dude!

Thumbnail by TheRedBeanie__ July 20, 2016

Thumbnail Syndrome 

The phenomenon in which someone seems far more attractive in the thumbnail version of a profile picture than they truly are.

I thought the girl who sent me a friend request was hot, but it turned out to be a case of Thumbnail Syndrome.

Thumbnail Syndrome by Ken_II July 27, 2009

Thumbnail Hot

When someone looks like they might be attractive in their Facebook or Twitter thumbnail until you click on it and find out that they're really not.

"Yeah, at first I thought he was really hot but turns out he was only thumbnail hot."

Thumbnail Hot by jeatags March 31, 2009

Rule of thumbnail 

A rule of thumbnail is a principle that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or determining if a Facebook profile is worth clicking on based on it's thumbnail.

Guy 1: Have you seen that chick's face?
Guy 2: No, i thought she wasn't worth looking at, according to my rule of thumbnail.

Rule of thumbnail by starterel March 21, 2013

thumbnail cheat 

n- a famous trick used on video sharing sites such as You tube, where users stick a random softcore porn picture (i.e. female assets and chicks seemingly engaged in sensual acts) in the middle of their videos so as to make that the default icon of the video, thus gaining views from easily excitable male users.

Such testosterone-pumped viewers click on the thumbnails, only to be disappointed by a completely random (and often ad-infested) video.

Not surprisingly, such videos often make it to the "Tio Viewed" list, thus exponentially increasing its number of victims.

To the horror of many, this can also be combined with being rick rolled.

Of course, females can be the victims of the thumbnail cheat as well (although more often out of curiosity than horniness.)

Note: I'm not trying to be sexist about guys in general. Still, how do you account for those millions of views on such videos or the pissed off comments left by male users? ;o

Male User: HELL YEA! Look at 'em jugs *clicks*

*Rick Astley's funkalicious "Never Gonna Give You Up" comes onto the screen*

Male User: NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
not this ginger again/ the thumbnail cheat!! *bangs head on desk*

thumbnail cheat by your average youtube user August 3, 2008