The Irish have lots of unique words that have no meaning in our American dialect. They also have a lot of words that mean something very different than what I, as an American, initially thought. Here are a list of words that I ran into that gave me some trouble:
Bespoke - "custom" or "boutique", as in Harold's Bespoke Tailor Shop
Banger - a breakfast sausage. Beware - they look like but do not taste anything like our sausage.
Bogger - a redneck, an uncouth, backwoods person
Braces - suspenders
Busker - a street performer. Dublin, especially, has oodles of buskers on their busy pedestrian shopping streets like Grafton Street.
Craic - pronounced "crack", means general goodness, as in "This party is craic! I'm glad I came."
Champ - mashed potatos with butter, sour cream, and scallions
Colcanon - same as champ, but with shredded cabbage
Colchie - a redneck
En Suite - a hotel room with its own bathroom. A suite in the USA is one that has all the amenities, such as jacuzzi tub, a kitchen, and a separate living room. Big difference!
Fanny - the king of all misunderstood words. Of course, in the USA, fanny is a totally inoffensive word meaning your rear-end or "bum" as they'd say in Ireland and the UK. However, there, fanny is a very vulgar word meaning a lady's, er, private parts. So do NOT say "Get your fanny down here!" to an Irish woman!
First Floor - second floor
Half-8, Half-7, etc - half past 8, half past 7, and so forth
Hoovering - vacuuming
Goujons - meat strips, as in "chicken goujons" meaning chicken nuggets
Knickers - ladies underwear, panties
Mac & Wellies - overcoat and galloshes
Nappy - diaper. Imagine the visual images this produced for those Irish who heard about Don Imus calling the Rugters b-ball team "Nappy-headed hos".
Nought - zero, pronounced 'not'
Pissed/locked/lashed/latched - drunk
Rubber - eraser
Slag - insult as in "She really slagged him down."
Soda - crackers, not to be confused with soft drinks (their term for Coke, Pepsi, etc)
Snog - kissed passionately, usually involving the tongue. When I first heard it, I thought it simply meant "kissed". However, I soon found out that you couldn't say "Come snog on your dad." Eeeew!
Starkers - naked
Sussed - figured out, thought about as in "He sussed it immediately."
Townie - an uppity city person
Zebra-crossing - crosswalk
Another amazing aspect of Ireland is that the accents are so different just one county way from each other. The people of Dublin, for example, are very easy to understand and at times almost sound Southern. The people of Cork, on the other hand, speak much faster, in sigher tones, and with a much stronger sing-song rhythm. Cork, as just one example, had many of its own usages and slang, such as:
Langer - a jerk, someone you don't think very highly of
Spanner - also a jerk, a.k.a. a tool
Allergic - bad, as in "The pub scene at McGerks was allergic"
Haunted - good, as in "So we left McGerks and went to O'Malleys. And O'Malleys was completely haunted!"
It was great fun to spend a lot of time with the Irish. I really enjoyed the pub culture and hanging out with people without being slaves to the TV. Another thing that was a lot of fun was that many pubs kept various instruments on hand. People would walk up, grab an instrument, and play a few songs. Many times, others would join in, with each person leading the choice of songs through 3 or 4 tunes.
It was loads of fun!