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• aa
  aa

  noun

  basaltic lava having a rough surface.
• AA
  AA

  abbreviation

  administrative assistant.
• a̅a̅
  a̅a̅

  (in prescriptions) ana.
• a.a.
  a.a.

  abbreviation

  author's alteration. Also A.A., AA
• A.A.
  A.A.

  abbreviation

  Alcoholics Anonymous.

aa

¹ American  

[ah-ah] / ˈɑ ɑ /

Or a'a,

noun

1. basaltic lava having a rough surface.

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AA ² American  

abbreviation

1. administrative assistant.

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AA ³ American  

Symbol.

1. a proportional shoe width size, narrower than A and wider than AAA.

2. the smallest proportional brassiere cup size.

3. a quality rating for a corporate or municipal bond, lower than AAA and higher than A.

4. Electricity. a battery size for 1.5-volt dry cells: diameter, 0.6 inch (1.4 centimeters); length, 2 inches (5 centimeters).

5. British. a designation for motion pictures certified as unsuitable for children under 14 unless accompanied by an adult.

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a̅a̅ ⁴ American  

Or āa

Symbol.

1. (in prescriptions) ana.

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a.a. ⁵ American  

Or aa

abbreviation

1. author's alteration. Also A.A., AA

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A.A. ⁶ American  

[ey-ey] / ˈeɪˈeɪ /

Or AA

abbreviation

1. Alcoholics Anonymous.

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A.A. ⁷ American  

abbreviation

1. antiaircraft. Also AA

2. Associate in Accounting.

3. Associate of Arts.

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AA ¹ British  

abbreviation

1. Alcoholics Anonymous

2. anti-aircraft

3. Architectural Association

4. (in Britain) Automobile Association

5. (in Britain) Advertising Association

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symbol

1. (in Britain, formerly) a film that may not be shown publicly to a child under fourteen

aa ² British  

/ ˈɑːɑː /

noun

1. a volcanic rock consisting of angular blocks of lava with a very rough surface

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aa ³ British  

abbreviation

1. ana ¹

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aa Scientific  

/ ä′ä /

1. A type of lava having a rough, jagged surface. It is relatively slow moving in its molten state, advancing in the form of massive blocks with fissured and angular surfaces that ride on a viscous interior. The blocks range in size between the size of a football and the size of a house.

2. See Note at pahoehoe

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Etymology

Origin of aa¹

First recorded in 1855–60; from Hawaiian ʿaʿā

Origin of a̅a̅⁴

From the Greek word aná, with superscript bar representing the nasal consonant

Example Sentences

To recreate the original stuffed toy version of Roo, the baby kangaroo that appears in author AA Milne's Winnie-the-Pooh stories.

From BBC • Apr. 29, 2026

The famous toy bear Winnie took its name from a black bear in London Zoo, that was particularly popular with children, including the son of AA Milne.

From BBC • Apr. 25, 2026

Adaptive Abilities, or AA, is a category where cheerleaders with and without disabilities compete side-by-side.

From BBC • Apr. 22, 2026

All major UK competitions now offer contests for AA teams, and Wales and Scotland are also fielding teams at the world championships.

From BBC • Apr. 22, 2026

He emptied all his handheld video games and Josh's remote control cars, and called his grandma to tell her that all he wanted for his birthday in November was AA batteries.

From "Eleanor & Park" by Rainbow Rowell