Biol. capable of living under varying conditions; e.g., able to live independently and as a parasite
Origin:
Fr facultatif < L facultas: see faculty
See facultative in American Heritage Dictionary 4
adjective
Of or relating to a mental faculty.
a. Capable of occurring or not occurring; contingent.
b. Not required or compulsory; optional.
Granting permission or authority.
Biology Capable of functioning under varying environmental conditions. Used of certain organisms, such as bacteria that can live with or without oxygen.