/ Dictionary / Index T third base: Meaning and Definition of Find definitions for: third' base' Pronunciation: [key] — Baseball. Baseball. the third in counterclockwise order of the bases from home plate. the playing position of the fielder covering the area of the infield near this base. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Third Amendment third baseman Related Content Daily Word Quiz: resilient Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language