The specific meaning, according to the cited Wikipedia entry, is the splitting of the compression and air conditioning functions in a (decentralized) wall or window mounted air conditioner. Compression takes place outside, air conditioning inside.

In the US, as you probably know, you'd just call this a window or wall mounted air conditioner (unit), as opposed to central air conditioning. While it's possible that even in the US, this technical distinction exists, I have never heard of it. Also, in this context - sounds like a lease agreement - the distinction would probably be irrelevant. And a general US audience would most likely get confused by a 'split' air conditioner.