n. Side: used in some mathematical terms designating a line or diameter.n. A straight line drawn from the vertex of a conic at right angles to the transverse diameter, and having a length equal to the diameter of that circular section which is at the same distance from the vertex of the cone as is the plane of the conic.n. A serranoid fish, Lates niloticus, found in the Nile. It attains a large size and is used for food.