What is the meaning of Achromatic?

Free from color; transmitting light without color-related distortion.

Containing components such as achromatic lenses and prisms, designed to prevent color-related distortion.

Uncolored; not absorbing color from a fluid; -- said of tissue

Having only the diatonic notes of the scale; not modified by accidentals.

Being achromatic in subject

Source: wiktionary.org