also: bunch · stack · cluster · close
Two ways of putting receivers close together so defenders cannot line up on them individually. Bunch is a triangle, stack is one behind another, and both exist to beat man coverage.
2 meanings, all below. Jump to the one you heard.
Three receivers aligned close together in a triangle. The point is that a defender cannot take a clean leverage position on any one of them without giving up leverage on another, and defenders in man coverage cannot follow their assignments without running into each other.
Cluster and close are program-specific names for the same idea or for near variants of it, and bunch is the common parent term.
cluster, closestack, tripsTwo or more receivers aligned directly one behind another. Where a bunch creates traffic, a stack creates ambiguity: a defender can only align on one of them, and the one he does not align on gets a free release.
It is the cheaper version of the same idea, needing two players rather than three. It is available out of formations a bunch is not.
stacked receiversbunchThe candidate list surfaced stack as a question asked against bunch, which is a good sign the pair is where the confusion lives rather than either term alone.
Effective at youth level for a slightly different reason than at higher levels: young defenders are usually taught to align on a man and have not been taught what to do when that becomes impossible.