inconsideration(n = noun.attribute) inconsiderateness, thoughtlessness - the quality of failing to be considerate of others;
is a kind of unkindness
has particulars: tactlessness, bluntness
Antonym: consideration

   Lack of due consideration; inattention to consequences; inconsiderateness. [1913 Webster]
"Blindness of mind, inconsideration, precipitation." [1913 Webster]
"Not gross, willful, deliberate, crimes; but rather the effects of inconsideration." [1913 Webster]

N  inattention, inconsideration, inconsiderateness, oversight, inadvertence, inadvertency, nonobservance, disregard, supineness, etourderie, want of thought, heedlessness, insouciance, abstraction, absence of mind, absorption of mind, preoccupation, distraction, reverie, brown study, deep musing, fit of abstraction, inattentive, unobservant, unmindful, heedless, unthinking, unheeding, undiscerning, inadvertent, mindless, regardless, respectless, listless, blind, deaf, bird-witted, hand over head, cursory, percursory, giddy-brained, scatter-brained, hare-brained, unreflective, unreflecting, ecervele, offhand, dizzy, muzzy, brainsick, giddy, giddy as a goose, wild, harum-scarum, rantipole, highflying, heedless, careless, inconsiderate, thoughtless, absent, abstracted, distrait, absentminded, lost, lost in thought, wrapped in thought, rapt, in the clouds, bemused, dreaming on other things, musing on other things, preoccupied, engrossed, daydreaming, in a reverie, off one's guard, napping, dreamy, caught napping, disconcerted, distracted, put out, inattentively, inadvertently, absent-mindedly, per incuriam, sub silentio, Int, stand at ease, stand easy!, the attention wanders, one's wits gone a woolgathering, one's wits gone a bird's nesting, it never entered into one's head, the mind running on other things, one's thoughts being elsewhere, had it been a bear it would have bitten you.