adjective

1. At fault; failing to fulfill responsibility, duty, or obligations.

   “I would certainly be remiss if I did not give credit where credit was due.”

2. Not energetic or exact in duty or business; careless; tardy; slack; hence, lacking earnestness or activity; languid; slow.

Synonyms: at fault, blameworthy, lash, lax, negligent, reprehensible, careless, languid