Miscible liquids mix together to form a homogeneous solution without a meniscus forming, according to Reference.com. Immiscible liquids form two separate layers with a curved meniscus and are considered to be unmixable. An example of two immiscible liquids is water and olive oil.
Liquids whose attractions between each other are weaker than attractions between their own molecules tend to be immiscible liquids. Many liquid mixtures are "partially miscible," which means that while they form two separate layers and a meniscus, the volume of each liquid's layers is not identical to the original volume of each liquid. Certain organic acids mix with water to form partially miscible liquid mixtures.