subcritical
Concise Oxford English Dictionary © 2008 Oxford University Press:
subcritical/sʌbˈkrɪtɪk(ə)l/
▶adjective Physics
- 1 (in nuclear physics) containing or involving less than the critical mass.
- 2 (of a flow of fluid) slower than the speed at which waves travel in the fluid.
'subcritical' also found in these Oxford entries:

