Source : Webster's Revised Unabridged Dictionary (1913)

Syntonizer \Syn"to*niz`er\, n. (Physics)
   One that syntonizes; specif., a device consisting essentially
   of a variable inductance coil and condenser with a pair of
   adjustable spark balls, for attuning the time periods of
   antenn[ae] in wireless telegraphy (called also {syntonizing
   coil}).