1) Body substance 
• (n.) Tissue which is not stained by fluid dyes.
A·chro'ma·tin noun (Biol.) Tissue which is not stained by fluid dyes. W. Flemming. 
Type: Term Pronunciation: ă-krō′mă-tin Definitions: 1. The weakly staining components of the nucleus, such as the nuclear sap and euchromatin.
[n] - the part of a cell nucleus that is relatively uncolored by stains or dyes
achromatin The part of a cell nucleus which does not stain readily with basic dyes.
noun the part of a cell nucleus that is relatively uncolored by stains or dyes