from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Morally or legally constraining; binding.
- adj. Imposing or recording an obligation: a bill obligatory.
- adj. Of the nature of an obligation; compulsory: Attendance is obligatory. Mathematics is an obligatory course.
- adj. Biology Obligate.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Imposing obligation, morally or legally; binding: an obligatory promise.
- adj. Requiring a matter or obligation.
from the GNU version of the Collaborative International Dictionary of English
- adj. Binding in law or conscience; imposing duty or obligation; requiring performance or forbearance of some act; -- often followed by on or upon.
from The Century Dictionary and Cyclopedia
- Imposing obligation; binding in law or conscience; imposing duty; requiring performance of or forbearance from some act: followed by on before the person, formerly by to.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. required by obligation or compulsion or convention
- adj. morally or legally constraining or binding
From Latin obligare obligate, from ob- to + ligare to bind, from Proto-Indo-European *leig- to bind. (Wiktionary)