The quality or condition of being resonant: words that had resonance throughout his life. Richness or significance, especially in evoking an association or strong emotion: "It is home and family that give resonance . . . to life\u201d ( George Gilder). "Israel, gateway to Mecca, is of course a land of religious resonance and geopolitical significance\u201d ( James Wolcott). Physics The increase in amplitude of oscillation of an electric or mechanical system exposed to a periodic force whose frequency is equal or very close to the natural undamped frequency of the system. Physics A subatomic particle lasting too short a time to be observed directly. The existence of such particles is usually inferred from a peak in the energy distribution of its decay products. Acoustics Intensification and prolongation of sound, especially of a musical tone, produced by sympathetic vibration. Linguistics Intensification of vocal tones during articulation, as by the air cavities of the mouth and nasal passages. Medicine The sound produced by diagnostic percussion of the normal chest. Chemistry The property of a compound having simultaneously the characteristics of two or more structural forms that differ only in the distribution of electrons. Such compounds are highly stable and cannot be properly represented by a single structural formula.