The term comes from employment and public accommodation law rather than web accessibility specifically, but it’s a useful lens for digital contexts too: providing a document in an accessible format on request, or offering a phone-based alternative to an inaccessible online form, can function as a reasonable accommodation while a permanent fix is in progress.
It’s generally treated as a stopgap, not a substitute for building accessible digital experiences in the first place, since case-by-case accommodations don’t scale and can themselves create delay and inequity.