The FSF has a process to approve licenses they consider free. OSI has a process to approve licenses that they consider open.
A requirement for the FSF to consider a license free is that it is open, so all free licenses are open source licenses.
But not all licenses that have been approved by the FSF have also be approved by OSI. Usually this is because they haven't sought out OSI approval. Does no OSI approval make it less open sourcy? I wouldn't say so. But it's difficult to be exact around vaguely defined concepts.
I'd say that in general, saying Open Source Software includes all Free/Libre software and more, so the term you're looking for is open source software.
If you only consider that software open source that has a license that has been approved by the OSI, this doesn't hold anymore.
There is no singular term for software that is licensed under a license approved by the OSI other than "software licensed under an OSI approved license". Nor is there a singular term for software licensed under a license approved by the FSF other than "software licensed under a FSF approved license".
So if you want the "fuzzy" definition (like F(L)OSS in itself is a fuzzy definition) just use open source software or OSS.
If you want to mean only licenses approved by the FSF or OSI, you'll have to go with the more cumbersome "Software under a FSF or OSI approved license"