What does ICYMI mean??
Oh well, I guess I might as well go ahead and admit that I am one of the slowest guys on the Internet. I mean, five minutes ago I had not a clue what "ICYMI" meant. I got an email from a big-deal group in Washington and the subject line started out with "ICYMI –".
Lucky for me, enlightenment was just a Google click away. The acronyms section of "The Free Dictionary" web site has a page that tells me that it stand for "In Case You Missed It." Ah... okay... yes, I had missed it, but now I know.
Hmmm... I wonder how long I have been missing it?
There is a Wiktionary page for ICYMI that dates to October 2009. Technically, it is an "initialism."