Cold pressed oils, also known as cold expeller pressed oils, are oils obtained by mechanically pressing the oily parts of the plants in a temperature controlled environment.
The friction, necessary for this process, causes temperatures to rise, the harder the plant being pressed, the higher the temperatures can get, temperatures can not rise above 120°F (49°C) for any oil to be considered cold pressed.
This process is not as efficient as using heat and hexane, but the oil remaining from cold pressed seeds, nuts or vegetables has no trace farm chemicals, no hexane molecules, no poisonous trans fatty acids.
More oil can be extracted if heat and chemicals are used. So most vegetable oil is not mechanically pressed in the traditional way. It is extracted, instead, with chemical solvents. Then it is boiled to evaporate the solvents, and then it is deodorized and bleached. The final product is very different from its natural source. The antioxidants are replaced by free radicals, and trans-fats appear in it.