mar·gin·ate (mär?j?-n?t?)tr.v. mar·gin·at·ed, mar·gin·at·ing, mar·gin·ates 1. To provide with or be a margin to; border.2. To add margin to (a stock portfolio).adj. marginate (-n?t, -n?t) also mar·gin·at·ed (-n??t?d) Biology Having a distinct border or edge.mar?gin·a?tion n.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.