Synonyms of negligent

1 Syllable
slow, lax, slack
2 Syllables
slowest, thoughtless, sloppy, heedless, slapdash, discinct, thriftless, laxer, unthought, remiss, slower, slipshod, mindless, reckless, offhand
3 Syllables
nonexpert, unthoughtful, hot-headed, neglectful, incautious, unthrifty, unwary, unthorough, unthinking, defaultant, nirvanic, unheedful, incurious, nonchalant, asocial, unbriefed, behindhand, unalert, unknowing, slovenly, delinquent, cursory, derelict, unmindful, amnesic, regardless, forgetful, nitwitted, oblivious, careless
4 Syllables
perfunctory, unexcited, improvident, devil-may-care, harum-scarum, amnemonic, unconcerned, dilatory, uninformed, nonobservant, unvigilant, unbothered, nonspecific, inadvertent, lamebrained, moratory, unaware, disregardful
5 Syllables
unimpressible, inattentive, unprofessional, unrecognizing, irreflective, tortoiselike, disimpassioned, pococurante, unreflective
6 Syllables
inconsiderate, uneconomical
7 Syllables
overventuresome