The phrase "replaceable battery" refers to a type of battery that can be taken out and replaced with a new one when it no longer holds a charge or stops working. Full definition
There is a 1560 mAh user replaceable battery included as well. (phoneradar.com)
It even comes with replaceable batteries in case your power goes out, so your home won't ever stop being smart. (geekwrapped.com)
Enjoy hours of entertainment on your Lumia 640 as it is powered by a 2500 mAh replaceable battery with up to 27.3 hours of talktime on 2G networks and up to 20.3 hours on 3G networks. (flipkart.com)