What does comment mean in French?

comment means how in French.

Note :- Comment means how when used in a sentence, but when used as a single Word may be different.

'Comment !!' translates to English as 'What ?' or 'What !!'. It might mean that the speaker understood your french, but didn't understand the underlying meaning. It could just mean that he didn't like what you said, and now wants to talk to you about Joan of Arc.