Synonyms for inadequate

abysmal, atrocious, awful, bad, below par, crummy, defective, deficient, dismal, dreadful, faulty, horrible, imperfect, inferior, insufficient, lacking, lousy, low-grade, mediocre, not good enough, not up to scratch, poor, poor-quality, second-rate, shoddy, suboptimal, substandard, terrible, unacceptable, unqualified, unsatisfactory, wanting, wretched