Pronunciation: (rē-ak'tuns),[key] —n. 1. Elect.the opposition of inductance and capacitance to alternating current, expressed in ohms: equal to the product of the sine of the angular phase difference between current and voltage and the ratio of the effective voltage to the effective current. Symbol: X Cf. capacitive reactance, inductive reactance. 2. Acoustics.See acoustic reactance.