By Harry Guinness, HowToGeek.com, July 13th, 2017
While you can block someone completely on Facebook, it’s a pretty dramatic measure.
Essentially, your Facebook account will cease to exist for them. If you’re just trying to get a bit of a break, you can unfriend them or block them from sending you Facebook Messages so they can’t contact you privately. Here’s how.
Open up a chat with the person you want to block.
Click on the Gear icon in the top right and select Block Messages…