Term used in place of Undertale when the content in question is NSFW.
Toby Fox, the developer of Undertale, invented the term in order to make it easy to distinguish between SFW and NSFW Undertale content.
Most frequently used as a tag for Rule 34 of Undertale.
/r/Undertail is a subreddit for Rule 34 of Undertale.
by Smerg the Dargon April 8, 2016
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Undertale NSFW tag. Usually used for porn, harsh words, blood.
"They are browsing through the undertail tag. I didn't know they liked undertale THAT much"
by boneme April 4, 2016
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a perverted blog of undertale thats really fucked up
person 1: fucking hell undertail fucked me up
person 2: undertale in general is fucked up
by tbh.septic March 18, 2016
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A sexual/NSFW Not Safe For Work version of Undertale. Never look it up for the love of your innocence.
I was dared to look up Undertail the other day... It scared me so much, I couldn't sleep. Never again, bro.
by PastelSonSpider February 12, 2016
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the DeviantArt tag that is used to separate NSFW and SFW art from the game/fandom UNDERTALE. The first one of these images was uploaded 4 days after undertale as a game released. I love this shitstain of a fandom I'm in
guy one: yo have you seen what the fandom has done to undertale?
guy two: yea, there's a whole other part called undertail, the art is actually pretty good.
guy one: have you...
guy two:
guy one:
by not william afton December 5, 2020
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Another universe for the hentai-filled game: Undertale. It is under the tail which is an asshole and it's basically furry hentai.
Undertail is hot as fuck.
by trans mans September 4, 2018
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