What is "polariton"

n. (context physics English) Any of a class of quasiparticles comprising elements of electromagnetic waves and excited states of matter

In physics, polaritons are quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation. They are an expression of the common quantum phenomenon known as level repulsion, also known as the avoided crossing principle. Polaritons describe the crossing of the dispersion of light with any interacting resonance.