crit·i·cal mass • n. Physics the minimum amount of fissile material needed to maintain a nuclear chain reaction. ∎ fig. the minimum size or amount of something required to start or maintain a venture: a communication system is of no value unless there is a critical mass of users.

critical mass Minimum mass of fissionable material required in a fission bomb or nuclear reactor to sustain a chain reaction. The fissionable material of a fission bomb divides into portions less than the critical mass; when brought together at the moment of detonation they exceed the critical mass. See also fission

Critical Mass ★★ 2000 (R)

This one will seem very familiar. Terrorist Samson (Kier) and his crew steal nuclear material and retreat to a deserted nuclear power plant in southern California in order to build a bomb. Only the power plant isn't so deserted and security guard Mike (Williams), aided by babe Janine (Loughlin), work to thwart Samson's nefarious plan. 95m/C VHS, DVD . Treat Williams, Udo Kier, Lori Loughlin, Blake Clark, Andrew Prine; D: Fred Olen Ray; C: Theo Angell; M: Neal Acree. VIDEO

critical critical mass originally, the minimum amount of fissile material needed to maintain a nuclear chain reaction. In extended usage, the minimum size or amount of resources required to start or maintain a venture.
critical path the sequence of stages determining the minimum time needed for an operation, especially when analysed on a computer for a large organization.