"Replay protection" is a security measure to prevent someone from using or repeating the same action multiple times. It ensures that certain actions or transactions can happen only once and cannot be duplicated or replayed again. Full definition
Unfortunately, any strong replay protection scheme requires a hard fork. (bitcointechtalk.com)
This is causing some anxiety as many believe this lack of replay protection will cause all sorts of horrible things on the network. (bitcointechtalk.com)
Firstly, we appreciate that they implemented replay protection to protect innocent users and businesses from accidentally losing money. (dailybitcoinnews.com)