Definition of "indeclinable"

indeclinable

adjective
not comparable
1. That one cannot decline; unavoidable.
  Quotations
  He'd planned to work a double shift Friday night, but Gladys Silverman's indeclinable invitation threw a hefty wrench into David's plans.
  1994, Helen R. Myers, To Wed at Christmas, page 101
2. (grammar, of a word) Not grammatically declinable.
noun
plural indeclinables
1. (grammar) A word that is not grammatically inflected.