Definition of accustoming:
(v) :
(transitive, often passive voice or reflexive, with to) To make familiar by use; to cause to accept; to habituate, familiarize, or inure.
(v) :
(intransitive, obsolete) To be wont.
(v) :
(intransitive, obsolete) To cohabit.
(n) :
(obsolete) Custom.