halftone

Short definition from Wiktionary

Noun

1. 1
   Synonym of semitone, half the interval between two notes on a scale.
2. 2
   A picture made by using the process of half-toning.
3. 3
   An intermediate or middle tone in a painting, engraving, photograph, etc.; a middle tint, neither very dark nor very light.

Verb

1. 1
   To reproduce a photograph or other continuous tone image by the use of dots of various sizes.