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Aa(ä) [from a word for "water" of the same Indo-European root as Lat. aqua], name of many small streams of N Europe and Switzerland. Aa, or a derivative of it, is a component part of hundreds of European place names.
aa(ä`ä): see lavalava
, molten rock that erupts on the earth's surface, either on land or under the ocean, by a volcano or through a fissure. It solidifies into igneous rock that is also called lava.
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Abbr. for the “Architectural Association, ” the largest school of architecture in England; address 34–36 Bedford Square, London, WC1B 3ES.
AA(1) (Auto Answer) See modem.
(2) (Double A) A common single-cell battery used in myriad devices from flashlights to electronic equipment of all variety. Like its triple A (AAA) cousin, it provides 1.5 volts of DC power. When used in series, the voltage is multiplied. For example, four AA batteries yield 6 volts.