Yeah I wonder why the thread is about Christians? Hmm...
If I was to answer though I'd say a Christian is who keeps the commandments and follows the example of Prophet Jesus (AS) as it is clearly recorded in the Bible. He kept fasts, he prayed with his forehead on the ground like all the other prophets in the Bible, he didnt eat pork or become drunk. He also grew a beard.
He remembered God at all times and testified that ultimate power and all knowledge is with God. He reveals it to whom he pleases. Knowledge like that of the last hour is only with God. He healed those blind, diseased and even gave life to the dead by the power God GAVE him.
The ironic thing is that as a Muslim I have NO problem with admitting any of the above. Infact it is perfectly inline with Islam