(KiloBits Per Second) One thousand bits per second. Kbps is used as a rating of relatively slow transmission speed compared to the common Mbps or Gbps ratings. Upper case "B" in KBps means kilobytes per second, but "b" for bit and "B" for byte are not always followed and often misprinted. KBps or KB/s would be used for earlier disk and tape transfer ratings as data are transferred in parallel, not serial.
A variation of the term is "K bps," with a space between the K and bps. In this case, it may mean exactly 1,000 bps in constrast to "Kbps" without the space which would be the binary 1,024 bps. This usage is not widely known or adhered to and most modem ratings use Kbps. For example, 56 Kbps means 56,000 bps and not 56 times 1,024 bps.
KiloBits per Second) Could also be KBs for kilobytes.