Synonyms of the word 
ACID-FAST → IMPERVIABLE - IMPERVIOUS
acid-fast
- adj. (histology, of bacteria) Retaining stain when treated with an acidic solution.
imperviable
- adj. impervious.
impervious
- adj. Unaffected or unable to be affected by.
- adj. Preventive of any penetration; impenetrable, impermeable, particularly of water.
- adj. Immune to damage or effect.
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