2. A toilet.
3. A hole in the surface of a bog. If you fall in a boghole you are liable to slide down into darkness and gunge and never come out again until someone cuts fuel in another fifty thousand years and ends up contacting an archaeologist.
4. In Ireland and perhaps elsewhere on the fringes of Europe or Canada, one of the most Godawful places you are ever likely to find yourself in. A tiny and usually misleading hint of civilisation in the middle of an endless brown or green but really grey landscape. Was probably so much nicer and more atmospheric before they decided to build houses. Typically used as a rest stop on a long bus journey for that very reason; people are less likely to get lost looking at the sights (because there are none) and forget they've got to catch the bus. If you grow up in a boghole, either you have an IQ of 2 or you have only one burning ambition in life from the cradle, and that is to get as far away from the boghole as you can, as soon as possible.
Oh, no, don't tell me little Sammy's gone for a walk and slipped and fallen down the boghole!
I grew up in Ballygronan. For me, the symbol of the promise held by the rest of the world was a tree growing on a nearby hilltop. Man, what a boghole.