Please note that I am aware of the usage "She wants to go to loo/toilet" but then it does not solve my purpose. Loo/Toilet is just a place but I want to specifically ask/tell that a kid wants to defecate.
In British English, "Go to the loo/toilet" doesn't just mean going to the room or the piece of furniture: it means using said piece of furniture. "Poop" is American; the British equivalent is "poo" but that's something you'd normally only say to a child.
For adults, in most situations, you don't need to say why somebody is going to the toilet: that's seen as private and people don't talk about it. You might excuse yourself from the room by saying that you're going to the toilet but the people you're talking to don't need or want to know exactly what you plan to do there. Saying where you're going serves more to inform them that you'll be back soon. As such, if adults do talk to each other about defecation, it's usually in either euphemistic ("doing a number two"), coarse ("taking a dump") or offensive ("going for a shit") terms. The main exception to this would be your doctor, who's likely to use terms like "defecate", "bowel movements" or "passing solids".
I was at some small place near Port Hope (Canada), and I asked for a washroom thinking that it's a general term. A guy there showed me the place and I went. I saw [urinals] but no [stalls].
Yes, washroom/restroom/bathroom (North America) or toilets/loos/bathroom (UK) is the general term. I've never seen a men's toilets with only urinals, anywhere I've been (UK, Europe, North America). It seems most likely that you missed the stalls/cubicles: perhaps they were behind a door that you mistook for a storage cupboard or something. In my experience, anywhere that has space has both urinals and stalls; anywhere that doesn't have space for both just has an ordinary toilet.
poop. – Owen Johnson Dec 09 '14 at 16:04