unforbidden

verb

1. a past participle of forbid.

adjective

2. not allowed; prohibited: a forbidden food in his religion.
3. Physics. involving a change in quantum numbers that is not permitted by the selection rules: forbidden transition.

adjective

1. not permitted by order or law
2. physics involving a change in quantum numbers that is not permitted by certain rules derived from quantum mechanics, esp rules for changes in the electrical dipole moment of the system