Mountain Climbing
noun, verbal noun
You've hopefully seen how 登る means "to climb." So, if you're climbing a mountain what is that? It's mountain climbing. In case you're wondering what the difference is between this and 登山, they are essentially the same. The main difference is that 山登り is a little less formal, and is generally used as a standalone word, whereas 登山 can be used in compound words like 登山家 (mountaineer).
やまのぼり
The reading comes from combining 山 and 登る together to form one word, 山登り. If you know the readings of those two words you know the reading of this word too.
山田さんって、山登りするんですか？
Do you go mountain climbing, Mr. Yamada?
先日、友人と山登りに行ってきました。
The other day, I went mountain climbing with a friend.
山登りをなめちゃいけないけど、山登りの後にソフトクリームをなめるのは最高です。
You shouldn't underestimate mountain climbing, but eating soft serve ice cream after a climb is the best.