Answer: I think the reference must be to a sus4 chord, also known as "suspended 4th." Someone just left off the "sus."

If so, that would be, from the bass upward, F, Bb, C. Or, with a seventh added: F, Bb, C, Eb. In a sus 4 the third of the triad is replaced by a 4th, which gives the feeling of wanting to move down and become a third in a following chord. Though in jazz, of course, it may never get its wish.

I'm assuming that this is being seen in some kind of pop or jazz reference. If it's a school harmony assignment there's a remote possibility that the reference is to a second inversion triad, normally known as a 6/4 chord: C, F, A.

But "sus4" is the more likely choice.