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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 June 19, 2016
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2
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 September 18, 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 June 25, 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 July 21, 2016
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