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lightfast

[lahyt-fast, -fahst]
adjective
  1. not affected or faded by light, especially sunlight; colorfast when exposed to light.
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Origin of lightfast

First recorded in 1955–60; light1 + fast1
Related formslight·fast·ness, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018