zero point

Short definition from Wiktionary

Noun

1. 1
   The location of the center of a burst of a nuclear weapon at the instant of detonation. The zero point may be in the air, or on or beneath the surface of land or water, depending upon the type of burst, and it is thus to be distinguished from ground zero.
2. 2
   Ground zero.
3. 3
   A children's game involving jumping over a chain of linked elastic bands.

Adjective

1. 1
   associated with zero on any scale, but particularly with a temperature of absolute zero