A consonant pronounced with a lowered velum, which allows air to go through the nose. In Irish it's generally represented by <m> and <n> and <ng>, though <nd> and <nc> can represent different nasals.
Could anyone help out with the pronunciation of "mionna". When I search for it using forvo, teanglann, or focloir.ie it doesn't come up with anything. Though, I think the latter tried to say it was a curse word....
EDIT: For those of you struggling with this, too: http://www.bitesize.irish/inirish/917