Definition
The cup is the front layer of a zone — the two or three defenders closest to the disc, working as a unit to apply pressure on the thrower and deny the most dangerous short throws. In a 3-3-1 arrowhead the front three form a triangle around the disc. In a 2-4-1 force-middle the front two are the cup.
In Context
The cup moves as a unit, not as individuals. When one cup player slides, the others slide with them — the shape stays consistent and the throws the cup is denying stay denied. A cup that breaks formation (one player chasing the disc while the others hold) is the most common way a zone collapses.
The cup's job is not to get a block — it is to take away the easy short forward throw and force the offence to throw over or through the middle. A held disc inside the cup is the cup winning; an attempted break shot that goes incomplete is the cup winning; a clean swing past the cup is the cup losing.
The cup tells the rest of the zone what to do. The mids and wings position relative to where the cup is set; the deep reads the cup's pressure to decide when to commit on a deep look.