I didn't realize until just now that we have 3girls and 4girls, and... isn't this a little ridiculous? I mean, where do we stop? Can we just... replace it all with a tag like... "girls" ? For images of more than one or something?
In fact, 2girls definition has always been really fuzzy anyway. What about a tag like "platonic" instead for images of two or more people together in an entirely non-sexual and non-romantic context? That even covers images that happen to have guys, and then we could be rid of a tag like girls because platonic would give you all of those group of people images that wasn't somehow romantic. Plus we'd also have a means of searching romantically themed images that weren't yuri images.
Updated by memento mori