Oral agreement – this term refers to a valid and binding contract, which has been concluded not in writing and have not been signed or sealed, but concluded via verbal conclusion only between the parties, also known as “hand-shaking” or made via spoken words. The Law of Contracts precisely details which contracts could be concluded verbally only, but having absolutely valid legal force. Within the provisions of the Law of Contracts, only certain types of contracts could be concluded as parole contracts. A synonym is “mouth contract”, “parley contract” and “verbal contract”. An antonym is “written agreement”.
See also http://www.legalzoom.com/business-law/contract-law/oral-contracts-do-they-carry .