habitually or characteristically accepting or tolerant of something, as social behavior or linguistic usage, that others might disapprove or forbid.

granting or denoting permission

a permissive nod.

optional.

Genetics . (of a cell) permitting replication of a strand of DNA that could be lethal, as a viral segment or mutant gene.

adjective

intolerant , mean , strict

adjective

acquiescent , agreeable , allowing , approving , easy-going , forbearing , free , indulgent , latitudinarian , lax , liberal , open-minded , permitting , susceptible , tolerant