indispensable

indispensable is an   Adverb

Definition:

[1] Not dispensable; impossible to be omitted, remitted, or spared; absolutely necessary or requisite.

[2] Not admitting dispensation; not subject to release or exemption. [R.] The law was moral and indispensable. Bp. Burnet.

[3] Unavoidable; inevitable. [Obs.] Fuller.

Synonyms: