waves - In order for the occurence of beat, why is it compulsory that $|{omega_2 - omega_1}| ll omega_1 + omega_2$?

As A.P.French in Vibrations and Waves writes,

The beating effect is most easily analyzed if we consider the addition of two SHM's of equal amplitude:

$$\mathbf{x_1} = \mathrm{A} \cos{\omega_1 .t} \& \mathbf{x_2} = \mathrm{A} \cos{\omega_2 .t}$$ . . . Clearly their addition,as a purely mathematical result,can be carried out for any values of $\omega_1$ & $\omega_2$. But its description as a beat phenomenon is physically meaningful only if $|{\omega_2 - \omega_1}| \ll \omega_1 + \omega_2.$

Why is it so? What does the author want to say??