Please do NOT respond if you’re not familiar with this word. Tell me what you say ONLY if you have heard other people use it in English, and particularly if you commonly use it yourself in English.
If you are a speaker of Irish please tell me how you pronounce it in Irish, too.
I should explain that Nicholas Jones wrote to me pointing out that LPD
doesn’t have ‘uillean (pipes)’, [a word] that is guaranteed to give English speakers problems. Collins English Dictionary gives only /'u:lɪən/. I may be wrong – I guarantee nothing – but I thought it was more commonly /'i:lɪən/.
In my reply I mentioned that Wikipedia says it’s pronounced ˈɪlən. This is also what is given on an American website for enthusiasts. I have now looked it up in the online OED, too, where I find the pronunciation given only as ˈɪljɪn.
Etymologically, the word appears to be the genitive singular of the Irish word for ‘elbow’, variously given in the nominative singular as uillinn (my Learner’s English-Irish Dictionary, and online here) or uille (Wikipedia, the OED s.v. union pipes, and the image shown alongside). Another source says it is an adjective meaning ‘acute-angled, having a sharp elbow or angle’. However, as the Wikipedia article recounts, it is also possible that it is really a reworking of the English word union.
To hear what uillean pipes sound like, go here and follow the links on the righthand side; or here.
Meanwhile I’ll ask around at the EFDSS and the London Irish Centre.