Definition of "undimmed"

But the importance of the railways as main arteries of the national economy remains undimmed, just as their fascination for the railway enthusiast is surely undiminished.

1951 April, D. S. Barrie, “British Railways: A Survey, 1948-1950”, in Railway Magazine, number 600, page 232

As I studied the songs that Kaczerginsky had compiled, I was struck not only by the pathos, sadness, and helpless feelings of authors both known and unknown, but also by the often undimmed spirit, hopefulness, and visions of a brighter future.

2017, Velvel Pasternak, Behind the Music, Stories, Anecdotes, Articles and Reflections, page 187