/ Dictionary / Index M Merthyr Tydfil: Meaning and Definition of Find definitions for: Mer•thyr Tyd•fil Pronunciation: (mûr'thur tid'vil Welsh mer'thir tud'vil), [key] an administrative district in Mid Glamorgan, in S Wales. 61,500; 43 sq. mi. (113 sq. km). a city in this district. 55,215. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Merthiolate Merton Related Content Daily Word Quiz: immense Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language