Pronounciations vary from region to region but Nollag Shona Dhuit (Nuh-lug Hun-nah gwit) in the singular and Nollag Shona Dhaoibh (Nuh-lug hun-nah gweeve (or maybe yeeve)) in the plural.

Or if you're feeling particularly brave try Nollag faoi shéan agus faoi mhaise (nuh-lug fwee hayne ogg-gus fwee wash-sha) which means a peaceful and (faoi mhaise translates as blessed or prosperous) Christmas.

Nollaig Faoi shéan agus ath bhlian faoi mhaise do gach éinne ar an Mhudcat ó Deaglán. Go meirimíd beó ag an am seo arís.

(I'm not doing phonetics for that but it means a Peaceful Christmas and a prosperous New Year to everyone on Mudcat from Declan. May we all be alive at this time again.)