Rain Boots
Rubber Boots, Riding Boots
noun
Long shoes aren't long in the feet part (that wouldn't make sense). Instead, the top part is long to keep you dry when it's raining. Yes, these are rain boots.
In modern Japanese, 長靴 usually means rain boots or rubber boots, and sometimes riding boots. But if you're referring to fashion boots or boots in general, you can just call them ブーツ.
The reading is a bit weird. Double kun'yomi, so think of it like 長い and 靴 are getting combined. 靴 also gets rendaku'd to ぐつ. Here's a mnemonic to remember that:
You call your rain boots gumboots, or g'oots (ぐつ) for short.
長靴をはく
to put on rain boots
長靴を脱ぐ
to take off rain boots
長靴を買う
to buy rain boots
長靴を洗う
to wash rain boots, to clean rain boots
コウイチはいつも雨の日はピカチュウの長靴をはいてくるよね。
Koichi, you always wear Pikachu rain boots on rainy days, don't you?
長靴って子供のものだけかと思ってたんだけど、最近じゃ大人用のオシャレな長靴も売ってるんだね。
I always thought rain boots were for kids, but these days they sell fashionable rain boots for adults too, don't they?
病院のベッドに横になりながら、彼は明日妻にいい乗馬用の長靴を買ってやろうと思った。
While laying in his hospital bed, he decided he would get a nice pair of riding boots for his wife the next day.
水たまりを見ると近づきたくなる。それが長靴効果。
Seeing a puddle makes you want to approach it. That's the Rain Boot Effect.