Integrated Circuit. Insatiable Craving. Irrevocable Crust. Indifferent Creator. Ignatios of Constantinople. Instigating Crime. Irritating C**. Individual Contributor. Your guess is as good as mine!
It’s standard big corp parlance for a role that has no direct reports. Obvious terminology for anyone who has worked in an org with a moderate size HR or higher, but anyone else has probably never heard of it. I knew immediately that it meant Individual Contributor but I can easily see someone not knowing it if have never worked in BigCorp
Go on Blind and you'll see it used all the time, along with a flurry of other incomprehensible acronyms that make Silicon Valley the TV show seem more real than ever. Blind is probably the strongest representation of BigCo population on the internet in terms of percentage of users.
You'll see it in plenty of Reddit discussions as well. It just so happens that a good hunk of this site happen to work in the kind of environment that the acronym is used frequently so perhaps it's not entirely unreasonable to expect it to be well known.
I swear though, if you haven't been on Blind and you just visit it's like decoding another language with all the acronyms.