Synonyms for regardless

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1. Heedless

   negligent, careless, unobservant, unheeding, inattentive, reckless, inconsiderate, inadvertent, blind, unfeeling, deaf, neglectful, unmindful, mindless, insensitive, lax, indifferent, listless, uninterested, unconcerned.

   Antonyms alert*, attentive, watchful.

2. In spite of; usually used with of

   despite, aside from, distinct from, without regard to, without considering, at all costs, at any cost, leaving aside; see also although, but 1, notwithstanding.