filter that passes signals outside a certain frequency range, and attenuates signals within that range
A band-stop filter or band-reject filter is an electronic filter that blocks the frequency component of a signal within a certain range value, where it has its lower cutoff frequency and upper cutoff frequency. The frequency component outside that range of value will be passed on.
A band-stop filter
Signal being filtered with 1 and 100 rad/s cutoff frequencies band-stop filter (above)