n. The act of resounding, or the state or quality of being resonant.n. In acoustics:n. The prolongation or repetition of sound by reflection; reverberation; echon. The prolongation or increase of sound by the sympathetic vibration of other bodies than that by which it is originally produced.n. In medicine, the sound evoked on percussing the chest or other part, or heard on auscultating the chest while the subject of examination speaks either aloud or in a whisper.n. In electricity, the condition of an alternating electric circuit in which the capacity reactance equals or approximately equals the inductive reactance.n. In psychology: A term applied, in the James-Lange theory of emotion, to the complex of bodily changes reflexly aroused by the object which excites emotion. “The changes are so indefinitely numerous and subtle that the entire organism may be called a sounding-board.”n. By extension of meaning, the sympathetic arousal in oneself, as if by echo, of a state of feeling whose manifestations one is observing in another, or the course of which one is tracing in imagination, but of which one has had no direct and first-hand experience.