A raised, multi-way pots observation.

[TexArcher]

I don't see this as an obvious fold at all.

The first two players didn't raise, they just limped, they may not have anything. This is a raise to try to isolate the third player the vast majority of the time (unless you have a read that one or both of the first players likes to limp from early position with monster starting hands or something like that)...