Element number 85, the heaviest naturally occurring halogen. It is one of the most unstable elements in nature, with its longest half-life at only just over 8 hours, so much so that at any given time less than a gram is believed to exist in the entire Earth, making it also one of the rarest naturally occurring elements. Most notably, it is the only element which requires one to say both "ass" and "tit" in its name.
Chemist: "I've successfully isolated a few thousand atoms of astatine-210 in this chamber!"

Other guy: "lol, asstitine"
by StupidBunny August 13, 2014
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A highly unstable radioactive element, the heaviest of the halogen series, that resembles iodine in solution. Its longest lived isotope has a mass number of 210 and has a half-life of 8.3 hours.
"Oooh, I made Asta-*BOOOOOOOOOOOOOM*"
by Tarn June 05, 2005
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Number 85 on the periodic table, in between Polonium and Radon.

It is also a son of a bitch who hates immature fifth graders, as its symbol is At, Polonium's is Po, and Radon's is Rn, and Astatine is lodged in between the two, stopping the periodic table from saying PoRn, and therefore ruining the laughs of immature children worldwide.
Chetna, smoking a bong: Dude do you think Astatine was made by the government to stop the periodic table from saying porn

Lars, after a fit of painful coughing: Whoa dude
by Long Sohn Jilvers November 19, 2019
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