Definition of Resonance

Term in chemistry used to explain properties of the octet rule when a single Lewis structure is inadequate. Resonance structure is an average of two of more Lewis structures which differ only in the position of their electrons. These species are said to exhibit resonance.
(Physics) A phenomenon in which a vibration or other cyclic process (such as tide cycles) of large amplitude is produced by smaller impulses, when the frequency of the external impulses is close to that of the natural cycling frequency of the process in that system.