Today, the term “Spey cast” refers to a variety of casts, but what they all have in common is that the line forms a loop (commonly known as the D loop) beneath the rod tip during the backcast, with the leader and some of the line briefly touching the water’s surface before the forward cast is made. This contact of the leader and line with the water’s surface is referred to as the anchor
or the grip
, and it stops the rearward journey of the line and allows the weight of the D loop to load the rod for the delivery cast.
I call all casts that have these characteristics "Spey casts", by I recognize that various Spey casting styles have developed over the years, including Traditional Spey Casting, Scandinavian or Underhand Casting, and Skagit Casting. My Spey Handout Booklet linked on another thread on this board has a discussion of these Spey styles: spey booklet