To bring or place under obligation, moral or legal; to hold by a constraining motive.
- To bind, compel, or constrain by a social, legal, or moral tie. See Synonyms at force.
- To cause to be grateful or indebted; oblige.
- To commit (money, for example) in order to fulfill an obligation.
- Biology Able to exist or survive only in a particular environment or by assuming a particular role: an obligate parasite; an obligate anaerobe.
- Absolutely indispensable; essential.