The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
- Involving, dependent on, or controlled by several factors.
- Of, relating to, or caused by a pattern of familial inheritance resulting from multiple genetic or environmental factors or from a combination of both.
- mulˌti·fac·torˈi·al·ly adverb