O-ring
A small rubber ring that provides a water seal in faucets and other plumbing fittings.

Office of Thrift Supervision (OTS)
The regulatory and supervisory agency for federally chartered savings institutions.  Formally known as the "Federal Home Loan Bank Board"

One-year Adjustable Rate Mortgage
A mortgage whose interest rate changes yearly.  The rate is usually based on movements of a published index plus a specified margin.

Open house
A marketing tool where a listing agent opens a house to the public for viewing.

Open listing
A property given to a number of brokers to market at the same time.

Open space
Undeveloped land or common areas in a planned community reserved for parks, walking paths or other natural uses.

Option
A situation in which a buyer puts down money for the right to purchase a piece of real estate within a set time period but does not have an obligation to buy.

Option Arm Loan
A home loan where the borrower has multiple payment options each month.  Some options include negative amortization.

Option listing
A listing agreement with a clause that gives the listing broker the right to purchase the property.

Orange peel
A type of wallboard finish with a texture like that of an orange peel.

Original principal balance
The amount of principal owed on a loan before a borrower makes any payments.

Origination fee
A fee charged by most mortgage lenders to cover costs of arranging the loan.

Ostensible agency
An implied agency relationship not involving a written agreement or documentation.

Outbuilding
Any barn, shop, shed or other structure located on a lot in addition to a house or other main building.

Overflow plate
A small plate that covers an outlet near the rim of a sink or tub.

Overflow prevention switch
A special air-pressure switch in a dehumidifier that turns the unit off when water in the reservoir rises to a certain level.

Overhang
A protruding structural feature.

Over Improved property
Property that could not be sold at a price high enough to recoup the costs of improvements.

Owner financing
A transaction in which the seller of a property agrees to finance all or part of the purchase.