ob·sess (əb-sĕs, ŏb-)
v. ob·sessed, ob·sess·ing, ob·sess·es
To preoccupy the mind of (someone) excessively.
To have the mind excessively preoccupied with a single emotion or topic: The conference organizer obsessed over the smallest of details.
[Latin obsidēre, obsess-, to beset, occupy : ob-, on; see OB- + sedēre, to sit; see sed- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.