/ Dictionary / Index M Mr. Nice Guy: Meaning and Definition of Find definitions for: Mr. Nice Guy Pronunciation: [key] a typically pleasant, likable person who avoids causing trouble or dissension (sometimes used with Miss, Ms., or Mrs. instead of Mr. when referring to a female). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mRNA M roof Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language