unbleaching

From un- +‎ bleaching.

unbleaching (not comparable)

1. Not to be bleached away.
   • 1812, Lord Byron, “Canto I”, in Childe Harold’s Pilgrimage. A Romaunt, London: Printed for John Murray, […]; William Blackwood, Edinburgh; and John Cumming, Dublin; by Thomas Davison, […], →OCLC, stanza LXXXVIII:

     Let their bleach'd bones, and blood's unbleaching stain, / Long mark the battle-field with hideous awe.