aa

¹ American  

[ah-ah] / ˈɑ ɑ /

Or a'a,

noun

1. basaltic lava having a rough surface.

---

AA ² American  

abbreviation

1. administrative assistant.

---

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.

---

a̅a̅ ⁴ American  

Or āa

Symbol.

1. (in prescriptions) ana.

---

a.a. ⁵ American  

Or aa

abbreviation

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

---

A.A. ⁶ American  

[ey-ey] / ˈeɪˈeɪ /

Or AA

abbreviation

1. Alcoholics Anonymous.

---

A.A. ⁷ American  

abbreviation

1. antiaircraft. Also AA

2. Associate in Accounting.

3. Associate of Arts.

---

aa ¹ British  

abbreviation

1. ana ¹

---

aa ² British  

/ ˈɑːɑː /

noun

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

---

AA ³ British  

abbreviation

1. Alcoholics Anonymous

2. anti-aircraft

3. Architectural Association

4. (in Britain) Automobile Association

5. (in Britain) Advertising Association

---

symbol

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

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

---

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

Mr. Warsh is known as aa inflation hawk, which makes Mr. Trump’s nomination especially notable.

From The Wall Street Journal • Jan. 30, 2026

The analysis revealed that in many cases, changes in the environment, such as steepening slopes or increasing eruption rates, amplified the ripples, which could lead to runaway mixing—and the likely formation of aa.

From Science Magazine • Jun. 9, 2023

Peterson, D. W. & Tilling, R. I. Transition of basaltic lava from pahoehoe to aa, Kilauea Volcano, Hawaii: Field observations and key factors - ScienceDirect.

From Textbooks • Jan. 1, 2017

"Ranjish hee sahi," says one Facebook update, "dil hee dukhaane ke liye aa!"

From The Guardian • Jun. 14, 2012

"Such abominable, thieving iniquity, on the pairt o' a Government ca'ain' itself leeberal, I never hard o' in aa my life," said the indignant Squire.

From Two Knapsacks A Novel of Canadian Summer Life by Campbell, John