Definition of wavelength noun from the Oxford Advanced Learner's Dictionary

wavelength

noun
ˈweɪvleŋθ
 
; ˈweɪvleŋθ
 
 
1 the distance between two similar points on a wave of energy, such as light or sound2 the size of a radio wave that is used by a particular radio station, etc. for sending signals or broadcasting programmes
Idioms

be on the same wavelength

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be on somebody's wavelength

(informal) to have the same way of thinking or the same ideas or feelings as somebody elseWe work together but we aren't really on the same wavelength.