Definition of Regardless

Babylon English Dictionary
without consideration for possible problems, without regard to potential difficulties; anyway, in any case
heedless, inattentive, unmindful
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Regardless Definition from Language, Idioms & Slang Dictionaries & Glossaries
Webster's Revised Unabridged Dictionary (1913)
(a.)
Not regarded; slighted.
  
(a.)
Having no regard; heedless; careless; as, regardless of life, consequences, dignity.
  
Webster's Revised Unabridged Dictionary (1913), edited by Noah Porter. About
hEnglish - advanced version

regardless
register \reg"is*ter\ (?), v. t. (securities) to enter the name of the owner of (a share of stock, a bond, or other security) in a register, or record book. a registered security is transferable only on the written assignment of the owner of record and on surrender of his bond, stock certificate, or the like.

WordNet 2.0

Adjective
1. (usually followed by `of') without due thought or consideration; "careless of the consequences"; "the proverbial grasshopper--thoughtless of tomorrow"; "crushing the blooms with regardless tread"
(synonym) careless(p), thoughtless(p)
(similar) heedless, thoughtless, unheeding

Adverb
1. in spite of everything; without regard to drawbacks; "he carried on regardless of the difficulties"
(synonym) irrespective, disregardless, no matter, disregarding