From Strong's Concordance:
1) a magus
a) the name given by the Babylonians (Chaldeans), Medes, Persians, and others, to the wise men, teachers, priests, physicians, astrologers, seers, interpreters of dreams, augers, soothsayers, sorcerers etc.
The term is translated in the KJV (and others) as "wise men" because the Magi were the most educated people in their cultures. In the same way that modern chemistry is the direct result of the intelligence of late-Medieval alchemists. Their wisdom eventually gave us what we know to be right, even though we know they were mostly wrong.
In effect, a magus was a scientist before science existed.
The Bible doesn't say how many there were, but it must be more than one, since the word used is a plural. Christian tradition says there were three, because they gave three gifts. In reality, the author may have intended it to be anywhere from two to a couple dozen.