100% sure of it. Without a doubt. This slang is mostly used in Australia.
by Puzant December 9, 2003
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Deadset is an Australian slang term for being serious.
Derives from the Phrase “I’m serious “

Meaning to be serious.
“Mate deadset I will pay you back”

By Isaac
by Mr_Fitz February 20, 2018
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Predoninantly Aussie slang, used to enforce the certainty of ones opinion.
Often used to enchance harsh assessments of the character of others.
Dave: "That guy over there is my new boss. He is a fuckwit".
Robbo: "That bloke? He looks like a deadset fuckwit to me".
by Jas the Aussie November 7, 2008
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Australian slang, meaning 100% true, and legit
Michael Jordan is deadset the greatest basketball player I’ve ever seen
by bung up August 22, 2018
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The word used to describe the kind of scene of total and utter desolation, desomation and isolation. Usually uttered to either oneself or to a friend upon the arrival to a party that noone went to/everyone has already been to a totaled the place.

Taken from the British TV drama Deadset, in which the cast find themselves alone in the middle of a post-apocolyptic wasteland dressed in drag and not nearly crunk enough.
"Ah man, Jas' party was a total deadset, no drink, no drugs and nobody even showed up."
"Didn't stop you from projectile vomiting and stealing a TV though did it?"
"Heeeell no."
by KEEPING December 21, 2008
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Not only a fuckwit. A massive fuckwit. Powerfully offensive term. Normally they are extremely hard work to be around. You weighed have to remove yourself from their company or knock them out.
‘That guy singing about short people and picking his nose was a deadset fuckwit. About time someone punched him in the face.’
by adirtyword September 4, 2020
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