To filter a substance means to pass it through a device which is designed to remove certain particles contained in it.

A filter is a device through which a substance is passed when it is being filtered.

A filter is a device through which sound or light is passed and which blocks or reduces particular sound or light frequencies.

If light or sound filters into a place, it comes in weakly or slowly, either through a partly covered opening, or from a long distance away.

When news or information filters through to people, it gradually reaches them.

A traffic filter is a traffic signal or lane which controls the movement of traffic wanting to turn left or right.

To filter out something from a substance or from light means to remove it by passing the substance or light through something acting as a filter.