Abrupt change from one energy level to another, especially such a change in the orbit of an electron with the loss or gain of a quantum of energy.
A quantum leap.
A sudden alteration in the energy level of an atom or molecule.
Any sudden and extensive change or advance, as in a program or policy.
A change from one quantum state to another, as when an electron orbiting a nucleus moves from one shell to another with the loss or gain of a quantum of energy.