(1) filter exhibiting frequency selective characteristic that allows low-frequency components of an input signal to pass from filter input to output unattenuated all high-frequency components are attenuated.
(2) a tuned circuit designed to pass all frequencies below a designated cut-off frequency.
(3) a filter that passes signal components whose frequencies are small and blocks (or greatly attenuates) signal components whose frequencies are large. For the ideal case, if H(ω) is the frequency response of the filter, then H(ω) = 0 for |ω| > B, and H(ω) = 1 for |ω| < B. The parameter B is the bandwidth of the filter. A filter whose impulse response is a low-pass signal.