Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
One who farmed the taxes (e.g., Zacchaeus, Lk. 19:2
) to be levied from a town or district, and thus undertook to pay to the supreme government a certain amount. In order to collect the taxes, the publicans employed subordinates (5:27, 15:1, 18:10), who, for their own ends, were often guilty of extortion and peculation. In New Testament times these taxes were paid to the Romans, and hence were regarded by the Jews as a very heavy burden, and hence also the collectors of taxes, who were frequently Jews, were hated, and were usually spoken of in very opprobrious terms. Jesus was accused of being a "friend of publicans and sinners" (Lk. 7:34
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.