Definitions for "Larmor frequency"
(omega or nu) - the frequency at which magnetic resonance can be excited; given by the Larmor equation. By varying the magnetic field across the body with a gradient magnetic field, the corresponding variation of the Larmor frequency can be used to encode position. For protons (hydrogen nuclei), the Larmor frequency is 42.58 MHz/Tesla.
The precession frequency of a nuclear spin in a magnetic field. It depends linearly on the spin's magnetic moment and the strength of the field.
The frequency at which a magnetic nucleus comes into resonance in a magnetic field of given strength.