Indispensable

1. (ecclesiastical, obsolete) Not admitting ecclesiastical dispensation; not subject to release or exemption; that cannot be allowed by bending the canonical rules. [16th-17th c.]
2. (of duties, rules etc.) Unbendable, that cannot be set aside or ignored. [from 17th c.]
3. Absolutely necessary or requisite; that one cannot do without. [from 17th c.]

Synonyms

• requisite

Antonyms

• dispensable