Definitions for 900 number
Random House Webster's College Dictionary
a telephone number preceded by the three-digit code “900,” used to provide information or entertainment for a fee charged directly to the caller's telephone bill.
Origin of 900 number:
Name given to telephone numbers in North America for which an extra charge is assessed, part of which is returned to the owner of the number.
Origin: In the original North American Numbering Plan, phone numbers beginning with an area code of "800" were reserved for so called toll-free numbers, where the party receiving the call pays the charges. The telephone companies later developed a corresponding set of numbers beginning with the area code "900" which would permit the owner of the number to receive additional fees from the caller.