Someone who is a 'dry arse' or 'dry' is someone who backs out of drinking alcohol for a reason which is not legitimate.
Person X: I'm goin to get so pissed tonight. Are you?
Person Y: No, i'm gonna stick to lemonade, I don't want to get drunk.
Person X: You fucking dry arse!

Here, person Y is being a dry arse because he/she is backing out of drinking alcohol.
by Jonny Lignier December 7, 2006
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Someone who gets offended at a joke for no reason
"Mate sahra is such a dry arse"
"I know all you did was call her a puff"
by Biggingie September 5, 2020
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