/ Dictionary / Index O onlap: Meaning and Definition of Find definitions for: on•lap Pronunciation: (on'lap", ôn'-), [key] — n. Geol. the advance of a sea beyond its former shore. the layer or layers of sedimentary rock formed on a sea floor as a result of this advance. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. onkus onlay Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language