1 [at; unstressed uht, it]
(used to indicate a point or place occupied in space); in, on, or near: to stand at the door; at the bottom of the barrel.
(used to indicate a location or position, as in time, on a scale, or in order): at zero; at noon; at age 65; at the end; at the lowest point.
(used to indicate presence or location): at home; at hand.
(used to indicate amount, degree, or rate): at great speed; at high altitudes.
(used to indicate a direction, goal, or objective); toward: Aim at the mark. Look at that.
(used to indicate occupation or involvement): at work; at play.
(used to indicate a state or condition): at ease; at peace.
(used to indicate a cause or source): She was annoyed at his stupidity.
(used to indicate a method or manner): He spoke at length.
(used to indicate relative quality or value): at one's best; at cost.
be at (someone), to be sexually aggressive toward (a person): She's pregnant again because he's at her morning, noon, and night.
where it's at, Informal. the place where the most interesting or exciting things happen: Emma says that Rome is definitely where it's at now.

before 900; Middle English; Old English æt; cognate with Old Frisian et, Old Norse, Old Saxon, Gothic at, Old High German az, Latin, Old Welsh, Old Breton ad, Greek a- (< a pre-Hellenic IE substratum language), Oscan, Old Irish, Gaulish, Phrygian ad- Unabridged


2 [aht, at]
a money of account of Laos, the 100th part of a kip.

1950–55; < Lao; compare Thai ʔàt formerly, a copper coin worth one eighth of a füang, ultimately < Pali aṭṭha eight


variant of ad- before t: attend.


achievement test.



Symbol, Chemistry.


Atlantic time. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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World English Dictionary
at1 (æt)
1.  used to indicate location or position: are they at the table?; staying at a small hotel
2.  towards; in the direction of: looking at television; throwing stones at windows
3.  used to indicate position in time: come at three o'clock
4.  engaged in; in a state of (being): children at play; stand at ease; he is at his most charming today
5.  (in expressions concerned with habitual activity) during the passing of (esp in the phrase at night): he used to work at night
6.  for; in exchange for: it's selling at four pounds
7.  used to indicate the object of an emotion: angry at the driver; shocked at his behaviour
8.  slang where it's at the real place of action
[Old English æt; related to Old Norse at to, Latin ad to]

at2 (ɑːt, æt)
n , pl at
a Laotian monetary unit worth one hundredth of a kip
[from Thai]

the internet domain name for

the chemical symbol for
1.  astatine
symbol for
2.  Also: A ampere-turn

abbreviation for
attainment target

abbreviation for
1.  Also: atm atmosphere (unit of pressure)
2.  atomic

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

O.E. æt, common P.Gmc. (cf. O.N., Goth. at, O.Fris. et, O.H.G. az), from PIE *ad- "to, near, at" (cf. L. ad "to, toward" Skt. adhi "near"). Lost in Ger. and Du., which use their equivalent of to; in Scandinavian, however, to has been lost and at fills its place. At-home (n.) "reception of visitors"
is from 1745; baseball at-bat "player's turn at the plate" is from 1941. The colloquial use of at after where ("where it's at") is attested from 1859. In choosing between at church, in church, etc. at is properly distinguished from in or on by involving some practical connection; a worshipper is at church; a tourist is in the church. At last is recorded from late 13c.; adv. phrase at least was in use by 1775. At in M.E. was used freely with prepositions (e.g. at after, which is in Shakespeare), but this has faded with the exception of at about, which was used in modern times by Trollope, Virginia Woolfe, D.H. Lawrence, and Evelyn Waugh, but nonetheless is regarded as a sign of incompetent writing by my copy editor bosses.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

The symbol for the element astatine.

at- pref.
Variant of ad-.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
The symbol for astatine.
astatine   (ās'tə-tēn')  Pronunciation Key 
Symbol At
A highly unstable, rare, radioactive element that is the heaviest of the halogen elements. Its most stable isotope 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 Periodic Table.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Computing Dictionary

AT definition


at definition

1. commercial at.
2. The country code for Austria.

The Free On-line Dictionary of Computing, © Denis Howe 2010
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American Heritage
Abbreviations & Acronyms
  1. ampere-turn

  2. astatine

  1. achievement test

  2. advanced technology

  3. air temperature

  4. antitank

  5. Atlantic Time

  6. automatic transmission

  1. airtight

  2. atmosphere

  3. atomic

  4. attorney

The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Encyclopedia Britannica


radioactive chemical element and the heaviest member of the halogen elements, or Group 17 (Group VIIa) of the periodic table. Astatine, which has no stable isotopes, was first synthetically produced (1940) at the University of California by American physicists Dale R. Corson, Kenneth R. MacKenzie, and Emilio Segre, who bombarded bismuth with accelerated alpha particles (helium nuclei) to yield astatine and neutrons. Naturally occurring astatine isotopes have subsequently been found in minute amounts in the three natural radioactive decay series, in which they occur by minor branching (astatine-218 in the uranium series, astatine-216 in the thorium series, and astatine-215 and astatine-219 in the actinium series). Thirty-three isotopes are known; astatine-210, with a half-life of 8.3 hours, is the longest lived.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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