A(n) is a material that takes in a wave when the wave hits it.

Refractors and absorbers.

Explanation: Almost every material takes in (at least a fraction) of a wave when a wave hits it, where some frequencies or wavelengths may have a bigger percentage taken in.

For electromagnetic waves, a perfect conductor will only reflect the incident wave, and every other case will absorb a part and reflect others.

The type of materials that are "good" by absorbing/transmitting waves are called refractors.

There are other materials called absorbers, but those ones are used for "particles", and you may recall that the light, an electromagnetic wave, can also be viewed as a particle.