Mobile Subscriber Identification Number which is the last part of the International Mobile Subscriber Identity (IMSI).
Mobile Subscriber Identification Number is a number that is a Unique Identifier for a Mobile Device (Mobile Station) working under TIA standards for cellular and PCS technologies. (e.g. EIA/TIA–553 analog, IS–136 TDMA, IS–95 or IS-2000 CDMA).
Mobile Subscriber Identification Number may also be called the MSID (Mobile Station ID) or IMSI_S (Short IMSI).