What is "accretionary wedge"

n. (context geology English) The accumulation of surface sediment formed between a subducting oceanic crustal plate and a continental tectonic plate, as it is scraped from off the top of the oceanic crustal plate.

An accretionary wedge or accretionary prism is formed from sediments that are accreted onto the non- subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust but in some cases includes the erosional products of volcanic island arcs formed on the overriding plate.