Although it seems to lack any definite pattern, pseudorandom noise consists of a sequence of pulses that will usually repeat itself, albeit after a long time or a long sequence of pulses.
For example, in spread-spectrum systems, modulated carrier transmissions appear as pseudorandom noise to a receiver (a) that is not locked on the transmitter frequencies or (b) that is incapable of correlating a locally generated pseudorandom code with the received signal.
Source: from Federal Standard 1037C and from MIL-STD-188
see also Pseudorandom number sequence, Pseudorandom number generator