oblige

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To compel or require (someone) to do something, as by circumstance or legality.
• intransitive verb To make indebted or grateful.
• intransitive verb To do a service or favor for.
• intransitive verb To do a service or favor.

from The Century Dictionary.

• To bind; attach; devote.
• To bind, constrain, or compel by any physical, moral, or legal force or influence; place under the obligation or necessity (especially moral necessity) of doing some particular thing or of pursuing some particular course.
• To lay under obligation of gratitude, etc., by some act of courtesy or kindness; hence, to gratify; serve; do a service to or confer a favor upon; be of service to; do a kindness or good turn to: as, kindly oblige me by shutting the door; in the passive, to be indebted.
• Synonyms To force, coerce. To serve, accommodate.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb obsolete To attach, as by a bond.
• transitive verb To constrain by physical, moral, or legal force; to put under obligation to do or forbear something.
• transitive verb To bind by some favor rendered; to place under a debt; hence, to do a favor to; to please; to gratify; to accommodate.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb transitive To constrain someone by force or by social, moral or legal means.
• verb transitive To do someone a service or favour (hence, originally, creating an obligation).
• verb intransitive To be indebted to someone.
• verb intransitive To do a service or favour.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb provide a service or favor for someone
• verb bind by an obligation; cause to be indebted
• verb force somebody to do something