Most significant bit. The bit that has the most value in a binary number or data byte. In written form, this would be the bit on the left. For example: Binary 1110 = Decimal 14 In this example, the left-most binary digit, 1, is the most significant bit, here representing 8. If the MSB in this example were corrupt, the decimal would not be 14 but 6. See also: LSB.