Resistant to fading when exposed to light, washing, or other environmental conditions; retaining color permanently.
From colour + fast (meaning 'fixed' or 'secure'), a compound word combining two English elements. The word 'fast' in this sense comes from Old Norse 'fastr' meaning firm or secure, used metaphorically for dyes that won't come loose.
Colourfast became a major selling point for clothing in the early 20th century when synthetic dyes improved—before that, most clothes would fade dramatically, which is why people kept formal clothes in dark colors that aged more gracefully.
Complete word intelligence in one call. Free tier — 50 lookups/day.