Definition of "millionth" []

• The ordinal number matching the number million in a series. (noun)
• One of a million equal parts. (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.

• "Free radicals are very difficult to study due to their short life-times - measured in millionth's of a second."
• "And even at millionth, which is the mention number we've reached."
• "Photos: TF Hammerhead celebrates two 'millionth' gallon pumped"