Regardless means without paying attention to what stands in the way. Carry on regardless, regardless of cost, regardless of the weather.
It takes of when the obstacle is named and stands alone when it is not. Irregardless is a form some people use and many object to, on the grounds that the ir- and the -less cancel; regardless is the safe choice in writing.
1adverbregardlessWithout paying attention to what stands in the way.
“The weather was awful, but we carried on regardless.”
regardless is a manner.
Proto-Indo-European
*wer-
Anglo-Norman
reguard
Middle English
regard
English
regard
English, today
regardless
From regard + -less. regard comes from Middle English regard, regarde, reguard, from Anglo-Norman reguard, from regarder, reguarder. Attested in Middle English starting around the mid 14th century. reward; compare also guard, ward, guardian, and so on.
Etymology from Wiktionary, CC BY-SA