Dictionary.com
definitions

achromatin

noun

the material of the nucleus of a cell that does not stain with basic dyesCompare chromatin
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
achromatin in Medicine

achromatin

[ā-krō′mə-tĭn]

n.

The part of a cell nucleus that remains less colored than the rest of the nucleus when stained or dyed.
Related formsa•chro′ma•tin′ic adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.