It is a pejorative (a word used negatively against an idea or person). An "Ivory tower" is usually used to dismiss ideas coming from an academic institution (usually a university), with the claim being that people working in a university are insulated from the real world, and that their ideas are impractical for real world conditions. An example might be something like: "Those economists up there in their Ivory Tower don't understand what it is like to run a business and pay taxes" I hope that helps, let me know if you need me to explain something better. (I meant to put it as an answer, but hit comment the first time!)

ivory tower = seclusion or remoteness of attitude regarding real, every day problems. Politicians and academics are often described as living in ivory towers and not understanding what average people have to cope with everyday.

Ok! 「ぞうげ　の　とう（zouge no tou)」 This is the pronounciation of 「象牙の塔」!!!

Ho, really? Good to know! This really helps my Japanese, too. Could you tell me the pronounciation of 象牙の塔 then?

Hi Ellen! Thank you for the additional information which really helps for Chinese learners! In Japanese we say 象牙の塔. So we use same characters except for a Hiragana!!!