If you are intentionally trying to cause harm by saying something that is provably false and succeed at causing harm, that's defamation. There are four tests and you have to prove all of them:

> To prove prima facie defamation, a plaintiff must show four things: 1) a false statement purporting to be fact; 2) publication or communication of that statement to a third person; 3) fault amounting to at least negligence; and 4) damages, or some harm caused to the reputation of the person or entity who is the subject of the statement.

https://www.law.cornell.edu/wex/defamation

> But if you are intentionally trying to cause harm by what you say, that's defamation.

Absolutely not. It can't be defamation unless it's untrue, and it also can't be defamation unless it's injurious to your target's reputation.