Definition of "number one" []

• One that is first in rank, order, or importance. (noun)
• Slang One's own interests; oneself: watching out for number one. (noun)
• Informal The act of urinating. (noun)
• Informal Urine. (noun)
• First in rank, order, or importance: the number one team in the nation; our number one problem. (adjective)

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.

• "At 10:42 A.M. Pacific time, on Wednesday, November 30, 1960, Armstrong sat in the cockpit of the number one airplane high over Rosamond Dry Lake anxiously waiting to be launched in an X-15 for the first time."
• "His father, Harvey Bundy, had been number one in his class at Harvard Law School and served as special assistant to Secretary of War Henry Stimson during World War II."
• "After however many years of being Englands number one player?"