- In a definite manner; in a manner showing complete certainty.
- It was an accusation that he flatly denied.
- In a manner that shows no emotion.
- He replied flatly to the policeman's questions.
- In sense 1. the collocation is nearly always with a negative idea. To flatly deny. To flatly refuse. To flatly contradict. And so on, similarly.
in a manner showing complete certainty