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Abbreviation of millibar
Abbreviation of megabit
Abbreviation of megabyte
(Or "Mb") megabytes or megabits. When referring to the size or data transfer rate of a storage device which is accessed in multiples of eight bits (e.g. RAM, hard disk) this almost certainly means megabytes, but when referring to the data transfer rate of a communications system it probably means megabits. Some years ago, it is claimed, "MB" always meant megabytes and "Mb" meant megabits but recently this useful distinction has been lost.