1. Of, relating to, or suggestive of a proprietor or to proprietors as a group: had proprietary rights; behaved with a proprietary air in his friend's house.
2. Exclusively owned; private: a proprietary hospital.
3. Owned by a private individual or corporation under a trademark or patent: a proprietary drug.

1. A proprietor.
2. A group of proprietors.
3. Ownership; proprietorship.
4. A proprietary medicine.
5. One granted ownership of a proprietary colony.

[From Middle English proprietarie, owner of property, from Old French proprietaire and from Medieval Latin proprietārius, both from Late Latin, of a property owner, from Latin proprietās, ownership. See property.]

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.