Here are the definitions for the letter "o"

Oaxaca

A mild Mexican cows’ milk cheese that is nearly identical in taste to mozzarella. It, too, is a stretched-curd cheese, or pasta filata, but instead of a ball, Oaxaca is formed into the shape of a braid.

Off

A term referring to undesirable flavors or odors too faint or ill-defined to be more precisely characterized.

Oil Off

Refers to the separation of oil when cheese melts.

Oily

A descriptive term that may refer to body, aroma, and flavor. Cheese held out of refrigeration for extended periods may also appear oily.

Oniony

A flavour of onion that comes through in the cheese. This is usually due to the feed or grass that has been eaten by the animals. It is generally an unfavorable characteristic.

Open

A term applied to cheese varieties containing small, mechanical holes that develop as a result of the manufacturing process. The holes may be small or large, densely patterned or randomly scattered, and irregular in shape. The blue mold that grows in Blue cheese forms around the openings in the lightly pressed curd. Air is introduced through punctures made with steel pins into the cheese (see Mechanical Holes). Pin holes are not to be confused with the open eyes in Swiss-type cheeses caused by fermentation. See Close.

Open

Refers to the body or texture of a cheese that contains holes or openings.

ORKNEY

Scottish. A mild cheddar-like cheese, sometimes smoked.

Overripe

A term descriptive of cheese that has passed its ideal state of flavor development or that has become too soft.