I've been an IC at a company providing IC services to small companies in the buildings next to FAANG HQs. I've worked as an IC designer, have been involved in a lot of IC (obviously) and I also have several years of experience in IC. So clearly, ic wot ppl mean when they type IC.
As an IC on various forums for over a decade, I've only started commonly seeing this abbreviation in the past 2 years.
Just don't.