One that withholds agreement or consent upon which progress is contingent. (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.
Use "holdout" in a sentence
"The salad bar is still there on the right, the lone holdout from the City Market Cafe, which still rents part of the location."
"The Weekly Standard's John McCormack focused on a CBS report about threatening phone calls the holdout anti-abortion Michigan Democrat got after the president persuaded him to vote for the legislation."
"Calvin Johnson, miss more than a couple days since Bryan Westbrook was a long-term holdout in"