rectifier UK /ˈɹɛktɪfaɪə/US /ˈɹɛktɪfaɪɚ/ noun4 •Something that rectifies. •A device that converts alternating current into direct current; often a diode. •An instrument used for determining and rectifying the variations of the compass on board ship. •The activation function f(x)= max (0,x), where x is the input to a neuron. formsrectifiers