The Oxford Thesaurus An A-Z Dictionary of Synonyms - obligationn.

1) responsibility, duty, charge, burden, onus; accountability, liability, trust; demand, requirement, compulsion, Literary devoir: It was Frank's obligation to get the children home safely. Civil servants have an obligation to serve the people. I could never fulfil all my obligations. 2) constraint, requirement, contract, promise, pledge, bond, agreement, covenant: The company is under no obligation to replace a product because the customer dislikes its colour. I am under an obligation to her for introducing us. 3) debt, liability: Denby may be unable to meet all his obligations.