/ Dictionary / Index O orthohydrogen: Meaning and Definition of Find definitions for: or•tho•hy•dro•gen Pronunciation: (ôr"thu-hī'dru-jun), [key] — n. Physics, Chem. the form of molecular hydrogen in which the nuclei of the two hydrogen atoms contained in the molecule have spins in the same direction. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. orthography orthokeratology Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language