What Does Bryan Mean In Greek?

Your question is a little confusing. I suppose you think your name Bryan is of Greek Origin and thus you want to know what it means. However, the name Bryan is does not come from the Greek language. It is basically an Irish name of Celtic origin and it means "Strong" or "High". For reference see the link below"
en.wikipedia.org

As "Bryan" is not a greek name, it has no greek meaning.

The name "Bryan" is a variant of "Brian" which is of Irish and English origin, which possibly comes from an old Celtic world that means "noble" or "high". The name became popular in Ireland from the King Brian Boru, who was a 10th century high king of Ireland.

It means gangster