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Main Entry: 1Chris·tian
Pronunciation: 'kris-ch&n, 'krish-
Function: noun
Etymology: Latin christianus, adjective & n., from Greek christianos, from Christos
1 a : one who professes belief in the teachings of Jesus Christ

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So, using this definition, the answer would be "yes":

1) Someone could believe in MOST of the teachings of Jesus.
2) Someone could believe that the Bible has flaws in it's representation of Jesus.
3) Someone could interpret the "god-teachings" of Jesus in a mystical or symbolical, rather than literal sense.

But, to be honest and candid, if you don't belive in god, then you shouldn't call yourself a Christian -- because the normal understanding of that term, includes a belief in God.