(FH, FHSS) A variation of spread spectrum communications in which a sequence of pseudo random numbers control a frequency synthesizer, generating different carrier frequencies that "hop around" in the desired frequency range. The receiver tunes to the same sequence of carrier frequencies in synchronisation with the transmitter.
Frequency hopping spread spectrum was invented by Hedy Lamarr ("the most beautiful girl in the world", Samson and Delilah etc.) and the composer George Antheil. They held a patent filed in 1942.