Band-limited (to $B$ Hz)

A signal whose spectrum is exactly zero past some finite frequency $B$ .

A signal is band-limited to $B$ Hz if $\hat f(\omega)=0$ for every $|\omega|\ge2\pi B$ -- its spectrum is exactly zero past a finite frequency, not merely small. This is the hypothesis the Nyquist-Shannon sampling theorem requires; no real, finite-duration signal is ever exactly band-limited.

Examples

$\sin(2\pi\cdot100t)$ is band-limited to $B=100$ Hz -- its spectrum is two spikes at $\pm100$ Hz and nowhere else.