WordWeb Online

1. Worn and broken down by hard use
   "a decrepit bus...its seats held together with friction tape";
   - creaky, derelict, flea-bitten, run-down, woebegone
    
2. Lacking bodily or muscular strength or vitality
   "a decrepit old woman";
   - debile [archaic], feeble, infirm, rickety, sapless, weak, weakly

See also: frail, worn

Encyclopedia: Decrepit