Kilobit
A value of measurement, a kilobit, kbit, or Kb is equal to 1,000 bits. For example, a 56k modem is capable of transmitting 56,000 bits per second.
When the b is uppercase (KB), this refers to a kilobyte. see the kilobyte page for definition of a kilobyte.
Also see: Bits, KB, Kbps, Kibibit, Kilobyte, Hard disk drive definitions, Measurement