1. One that induces, especially a substance that is capable of activating transcription from specific genes within a cell.
2. A part or structure in an embryo that influences the differentiation of another part.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.