Source : Webster's Revised Unabridged Dictionary (1913)

Wattless \Watt"less\, a. (Elec.)
   Without any power (cf. {Watt}); -- said of an alternating
   current or component of current when it differs in phase by
   ninety degrees from the electromotive force which produces
   it, or of an electromotive force or component thereof when
   the current it produces differs from it in phase by 90
   degrees.