Backstory: I live round the corner from my gran and visit her often so thanks to me she has a vague grasp of what memes are and how they work. The other day when I was round at hers and she asked what memes were popular at the moment so I told her about the "OK boomer" meme. She knew what boomers were already so she was able to get the concept of this meme fairly easily.
Fast forward to today, I'm over at my gran's again, and she's on the phone to my aunt. They got into a disagreement over a slightly racist comment my aunt made the other day (my gran is very much against racism) and my gran eventually just said "OK boomer" and hung up.
I've never been so proud.
UPDATE: So I told my gran about this post and the reaction it got - she said she's glad that so many of you enjoyed her little joke and that it proves she's still young at heart. I agree with that 100%.