prestack

== English == === Etymology === From pre- +‎ stack. === Adjective === prestack (not comparable) Before stacking, in the context of seismic migration. === Noun === prestack (plural prestacks) (category theory) The category c is called a prestack over a category C with a Grothendieck topology if it is fibered over C and for any object U of C and objects x, y of c with image U, the functor from objects over U to sets taking F:V→U to Hom(F*x,F*y) is a sheaf.