Iso is short for Isolation. Any Iso play or formation usually involves cutters vacating a certain space to give other cutter(s) more space.
This could be a set play, or called by a Handler. From there, the isolated player uses the extra space to get open and catch the disc.
The iso is used against man defense. The space is created when the defenders vacate the area to defend their checks.
The iso requires the isolated player to win the battle against their defender. It's a trade-off between giving the handler more options, or give the cutter more space.
 Uses for the Iso
- Prevent poaching. If a defense poaches often, an iso play is an effective counter. Any defenders that might have been poaching are cleared out by the players they are guarding.
- Exploit a weakness. The Iso forces a defender to cover a cutter one-on-one. If a player is weak defensively, an effective strategy would be to use their cutter as the isolated player.
- Make an easier throw. If a team has weak handlers, an iso would reduce the difficulty of the throw, providing the cutter gets open. It also reduces the number of players the handler has to keep track of.
 Forms of the Iso
One way to run an iso near the endzone is to call how many players are allowed in the endzone to cut. The rest of the team positions themselves behind the thrower removing themselves from the play.
Flooding is a variant of Iso.
 Defending Against the Iso
Plays or formations that rely on isolation are vulnerable to zone defence.
Any player defending an isolated player is being challenged by the other team. A competitive defender will try their very best not to allow the isolated player to get open. From there, the offense will have to dump the disc.
Cutters who have cleared out are out of the play and are not expected to catch the disc. A good defender will squeeze the open space, while remaining able to defend their mark. If the defender squeezes too much, thier cutter will be left wide open.