I have never checked for it, @Maggie Mae ; but I think that it is called “ignore” on this forum. You do like Gloria said and click on the avatar of the person you want to block, and you have several options, the last one being to ignore that person. I think that this also stops them from sending you private messages, but I am not sure of that part because I have never used this function. Also, if someone is sending you unwanted PM’s, then report that person and @Ken Anderson can help you.
Thanks ! It's not someone sending me messages ... it's someone with control and anger issues that I can't seem to not see ... so I did what was suggested and now out of sight, out of mind ... it worked great !