Is it someone who proclaims to be one? Or someone who reads about it, or sits on cushion from time to time, someone who has Buddha statues, someone who tries to do good, a combination of the above, etc?
If a Buddhist, how does someone answer questions in a predominantly Christian society such as why isn't your Dad/Mom going to church with you? Why does does your Mom/Dad spend all that time meditating? Aren't you worried that they are going to hell?