Real Dictionary

heterodyne in American English
designating or of the combination of two different radio frequencies to produce beats whose frequencies are equal to the sum or difference of the original frequencies
to combine two different frequencies so as to produce beats
adjective: noting or pertaining to a method of changing the frequency of an incoming radio signal by adding it to a signal generated within the receiver to produce fluctuations or beats of a frequency equal to the difference between the two signals
intransitive verb: to produce a heterodyne effect
transitive verb: to mix (a frequency) with a different frequency so as to achieve a heterodyne effect

heterodyne in British English
verb: to combine by intermodulation (two alternating signals, esp radio signals) to produce two signals having frequencies corresponding to the sum and the difference of the original frequencies