Mar dhea 

As if. Yeah, right. A Gaelic language term often used in English to denote disbelief or implausibility of the preceding statement. Mar dhea renders the previous statement dubious, highly unlikely or untrue. The phrase is in common use in Ireland and among the Irish diaspora.

Dave drank 15 pints last night, mar dhea!
Jim is the best employee we've ever had, mar dhea!

Mar dhea by taberesc April 19, 2012

Mar dhea 

(Pronounciation: Mahr Yah)
From Irish Gaelic.
Sarcastic response or statement about the innacuracy of a sentence, as in "Yeah Right" or "As if".

-"I did not have sexual relationship with that woman"
-"Mar dhea !"

Mar dhea by An Sionnach Beag June 23, 2022