Meniscus: The word "meniscus" comes from the Greek and refers to a crescent-shaped structure. Today a meniscus is something that is shaped like a crescent moon or a croissant pastry.
A meniscus can be an anatomic feature. For example, the medial meniscus of the knee is a crescent-shaped cartilage pad between the two joints formed by the femur (the thigh bone) and the tibia (the shin bone). The meniscus acts as a smooth surface for the joint to move on. The medial meniscus is toward the inner (medial) side of the knee joint, as indicated here: