/ Dictionary / Index P Pioneer Day: Meaning and Definition of Find definitions for: Pioneer' Day" Pronunciation: [key] — U.S. Hist. U.S. Hist. a legal holiday in Utah on July 24 to commemorate Brigham Young's founding of Salt Lake City in 1847. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pioneer Pioneers, The* Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language