Merriam-Webster Collegiate Dictionary - rusty

 I. adjective  (rustier; -est)  Date: before 12th century  1. affected by or as if by rust; especially stiff with or as if with rust  2. inept and slow through lack of practice or old age  3.  a. of the color rust  b. dulled in color or appearance by age and use ~ old boots  4. outmoded  5. hoarse, grating  • rustily adverb  • rustiness noun  II. adjective  (rustier; -est)  Etymology: alteration of restive  Date: 1625 chiefly dialect ill-natured, surly