Ack-ack

Ack-ack-n (informal)
1- an antiaircraft gun
2-antiaircraft fire

Acinus

Acinus-n
1-a rounded sac, containing secretory cells, found at the ends of the ducts in an exocrine gland
2-see alveolus
3-one of the small globes (dropulets) that make up an aggregate fruit such as a blackberry or raspberry

Acidulous

Acidulous-adj
1-slightly sour in taste (formal)
2-cutting and sharp in speech or tone

Acidulate

Acidulate-vti
to make something slightly acid, or become slightly acid

Acicula

Acicula-n
a needle-shaped part, for example, a spine, bristle, or crystal (technical)

Acidophil

Acidophil/Acidophile-n
1-a microorganism or plant that fourishes in an acid environment
2-a cell that stains readily with acidic dyes

Achromatic

Achromatic-adj
1-without color and therefore white, gray, or black in appearance
2-able to reflect or refract light without spectral color separation
3-used to describe cells not easily stained with standard dyes
4-using a scale with no sharps or flats