Synonyms for Careless (same or very similar meaning)
WordNet sense 1 ((usually followed by `of') without due thought or consideration):
regardless
WordNet sense 2 (marked by or paying little heed or attention):
heedless, thoughtless
WordNet sense 3 (casually thoughtless or inconsiderate):
offhand, offhand
WordNet sense 4 (marked by insufficient care or attention):
negligent
WordNet sense 5 (carelessly failing to exercise proper caution):
incautious
WordNet sense 6 (characterized by careless unconcern):
reckless
WordNet sense 7 (marked by great carelessness):
sloppy
WordNet sense 8 (hasty and without attention to detail; not thorough):
casual, cursory, perfunctory
WordNet sense 9 (simple and natural; without cunning or deceit):
artless
From the ODE community, based on WordNet
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