/ Dictionary / Index R rift valley: Meaning and Definition of Find definitions for: rift' val"ley Pronunciation: [key] — Geol. Geol. graben. a subsea chasm extending along the crest of a mid-ocean ridge, locus of the magma upwellings that accompany seafloor spreading. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. rift-sawed Rift Valley fever Related Content Daily Word Quiz: clairvoyant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language