/ Dictionary / Index A actomyosin: Meaning and Definition of Find definitions for: ac•to•my•o•sin Pronunciation: (ak"tu-mī'u-sin), [key] — n. Biochem. a complex protein, consisting of myosin and actin, that is the major constituent of skeletal muscle and is thought to interact with ATP to cause muscle contraction. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: actomyosin (Thesaurus) act of war acton Related Content Daily Word Quiz: labyrinth Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language