[at; unstressed uh
t, it] 
| 1. | (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. |
| 2. | (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. |
| 3. | (used to indicate presence or location): at home; at hand. |
| 4. | (used to indicate amount, degree, or rate): at great speed; at high altitudes. |
| 5. | (used to indicate a direction, goal, or objective); toward: Aim at the mark. Look at that. |
| 6. | (used to indicate occupation or involvement): at work; at play. |
| 7. | (used to indicate a state or condition): at ease; at peace. |
| 8. | (used to indicate a cause or source): She was annoyed at his stupidity. |
| 9. | (used to indicate a method or manner): He spoke at length. |
| 10. | (used to indicate relative quality or value): at one's best; at cost. |
| 11. | be at (someone), to be sexually aggressive toward (a person): She's pregnant again because he's at her morning, noon, and night. |
| 12. | 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. |
[aht, at] | a money of account of Laos, the 100th part of a kip. |
| var. of ad- before t: attend. |
| 1. | achievement test. |
| 2. | antitank. |
| attotesla. |
| astatine. |
| Atlantic time. |
| am·pere-turn (ām'pîr-tûrn') n. Abbr. At A unit of magnetomotive force in the meter-kilogram-second system equal to the magnetomotive force around a path linking one turn of a conducting loop carrying a current of one ampere. |
| as·ta·tine (ās'tə-tēn', -tĭn) n. Symbol At 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. [Greek astatos, unstable; see astasia + -ine2.] |
| at 1 (āt; ət when unstressed) prep.
[Middle English, from Old English æt; see ad- in Indo-European roots.] |
| at 2 (ät) n. pl. at See Table at currency. [Lao àt, perhaps from Thai  àt, former coin worth one-eighth of a füang (a former unit of currency), ultimately from Pali aṭṭa, eight, from Sanskrit aṣṭā; see oktō(u)- in Indo-European roots.] |
| aT abbr. attotesla |
| At 1 The symbol for the element astatine. |
| At 2 abbr. ampere-turn |
| AT abbr.
|
| at·to·tes·la (āt'ō-těs'lə) n. Abbr. aT One-quintillionth (10-18) of a tesla. |
At
The symbol for the element astatine.
at- pref.
Variant of ad-.
AT
IBM PC AT
at
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2.
| aT attotesla |
At
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AT
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At
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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