The Larmor frequency aka the "gyrofrequency" is the frequency with which charge particles orbit in a magnetic field. It directly from the solution of the equations of motion:
[tex]\frac {d\vec v}{dt} = \frac {q}{m} \vec v \times \vec B[/tex]
I don't think you meant to include the factor of 1/2.
The term is also used to denote the rate of precession of a magnetic moment in a magnetic field such as an atomic nucleus. I gathered you meant the "gyrofrequency" from the form you displayed.