What does bonne matin mean in English?

'bonne matinée' = [have a] good morning

'de bon matin' = early in the morning

('bonne matin' is not grammatically correct)

the common greetings are 'bonjour' (from the morning to the evening) and 'bonsoir' (meaning more specifically good evening). You can say 'bonne matinée' when you are leaving somebody in the morning, but not to greet the people when you meet them.