1. In common usage the baud rate of a modem is how many bitsit can send or receive per second. Technically, baud is the number of times per second that the carrier signal shifts value - for example a 1200 bit-per-second modem actually runs at 300 baud, but it moves 4 bits per baud (4 x 300= 1200 bits per second). From Matisse

2. measures of the rate at which signals are transmitted over a telecommunications link. It is equivalent to the number of elements or pulses transmitted in one second. From Linux Guide @FirstLinux