magic circle

Short definition from Wiktionary

Noun

1. 1
   A circle marked by a practitioner of magic, used as magical protection or to form a magical area.
2. 2
   An arrangement of natural numbers on circles such that the sum of the numbers on each circle and the sum of numbers on diameter are identical.
3. 3
   The imagined space, separate from the real world, in which players in a virtual reality system experience immersion.

Proper noun

1. 1
   A British organization dedicated to promoting and advancing the art of stage magic.
2. 2
   Collectively, the five most prestigious London-headquartered multinational law firms: Allen & Overy, Clifford Chance, Freshfields Bruckhaus Deringer, Linklaters, and Slaughter and May.