/ Dictionary / Index O open system: Meaning and Definition of Find definitions for: o'pen sys'tem Pronunciation: [key] — Thermodynam. Thermodynam. a region separated from its surroundings by a boundary that admits a transfer of matter or energy across it. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. open string open-timbered Related Content Daily Word Quiz: lunar Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language