[more exactly; most exactly]
1 — used to stress that something is accurate, complete, or correct
The mansion has exactly 33 rooms.
I know exactly where they went.
The two rooms are exactly the same size.
When exactly are they supposed to arrive? = Exactly when are they supposed to arrive?
2 informal — used in speech to say that what someone has said is exactly correct or that you agree with it completely
“So you think we should take an earlier flight?” “Exactly.” [=yes, that's exactly what I think]
“It's just not worth the trouble.” “Exactly.”
3 : in a correct or precise way
The levers need to be exactly positioned.
: in a way that agrees completely with what is needed
You need to do exactly [=just, precisely] as you're told.
4 : in every way
That was exactly the wrong thing to do.
He is exactly what a good student ought to be.