Definition of "columbium" [co•lum•bi•um]

• Niobium. No longer in scientific use. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "These minerals are the principal sources of columbium (commonly called niobium), tantalum and molybdenum metals."
• "Possible substitutes for molybdenum as a strengthening alloy in steel include vanadium, chromium, columbium, and boron."
• "In the presence of columbium the solution first becomes blue and then changes to a turbid brownish-black"