acid-fast

[as-id-fast, -fahst]

adjective

1. resistant to decolorizing by acidified alcohol after staining.

acid-fast

adjective

1. (of bacteria and tissues) resistant to decolorization by mineral acids after staining

Other Word Forms

• acid-fastness noun

Word History and Origins

Origin of acid-fast¹

First recorded in 1900–05

Example Sentences

It is a powerful oxidising agent and rapidly destroys most bacteria, but tubercle and other acid-fast organisms resist its lethal action for considerable periods, and upon this fact the method is based.

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It belongs to that small group known as acid-fast bacteria.

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This method is supposed to differentiate between B. tuberculosis and other acid-fast micro-organisms.

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