1. a nonfading blue dye or pigment.
2. a person who is true-blue.
3. (in the 17th century) the color adopted by the Covenanters in contradistinction to the royal red.
Pronunciation: (trOO'blOO'), [key]
unwaveringly loyal or faithful; staunch; unchangingly true.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.