from The American Heritage® Dictionary of the English Language, 4th Edition
- n. 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. Atomic number 85; melting point 302°C; boiling point 337°C; valence probably 1, 3, 5, 7. See Table at element.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A highly radioactive chemical element (symbol At), one of the halogens, with atomic number 85.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium
Greek astatos, unstable; see astasia + -ine2.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek ἄστατος ("unstable") + -ine. (Wiktionary)