Definition of offlap in English:

offlap

noun

Geology
  • A progressive diminution in the lateral extent of sedimentary deposits in passing upwards from older to younger strata, so that each stratum leaves a portion of the underlying one exposed; a set of strata exhibiting this, typically as a result of regression of a shoreline. Contrasted with onlap.

Origin

Early 20th century; earliest use found in Amadeus William Grabau (1870–1946). From off + lap, after overlap.

Pronunciation

offlap

/ˈɒflap/