CirMet is a magic Runeword created by combining a Cir Rune of Ritual and a Met Rune of Invocation.
How to Create CirMet
You can create CirMet by adding the magic Cir Rune of Ritual and the magic Met Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Cir - Cast the same non-Channeled Skill 3 times in a row. (50)
Met - You leave the Necromancer's Desecrated Ground behind you for 3 seconds, dealing damage to enemies within. (100)
Overflow
CirMet can not overflow because the amount of Offering you receive from the Cir Rune exactly fills the required Offering of the Met Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.