De Witt (d? w?t?, v?t?), Jan 1625-1672. Dutch politician. He and his brother Cornelius (1623-1672) were murdered by an angry mob for their opposition to William of Orange.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.