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!
by TheRedBeanie__ March 18, 2016
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1 - The nail of the thumb
2 - Something that is small or brief; concise
3 - A printing; small and rough
1 - Look at Joe's bleeding thumbnail!
2 - Jane quickly wrote a thumbnail summary of the chapter she had read.
3 - Bob drew a thumbnail sketch of his idea before he started his actual picture.
by 7sdrawkcab May 4, 2009
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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!"
by ibbit June 29, 2009
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term used to describe a person that appears to be attractive in a thumbnail picture on a social networking website, however, the full size image reveals their ugliness.

sometimes used to describe if you would have sex with the person if they did, in fact, look how they do in the thumbnail image.

goes along with the trend of people always placing the image they look best in as their profile picture.
I was browsing Facebook today and ran across what i thought was a cute girl. She looked good in the small picture, but once I clicked on it I found out she was a thumbnailer.
by Linger May 20, 2009
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Describes a person who is very attractive in their internet thumbnail, but turns crazy ugly the second it is enlarged to full size.
That girl is ugly, but her facebook page makes her look thumbnailable.
by HoneyBee123 June 1, 2009
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the little pictures that make looking at porn so much easier and simplier
i looked at all the thumbnails of the dirty bitch
by themainevent November 18, 2003
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