Streamlines refer to the smooth and efficient flow of a liquid or gas through a particular medium. Synonyms for this term include streamlined, aerodynamic, and hydrodynamic. Streamlined implies a shape that reduces drag or resistance, such as a car or airplane. Aerodynamic refers to an object's ability to travel through the air with minimal resistance, such as a rocket or a bird. Hydrodynamic is a term focused on the movement of liquids over surfaces, such as the hull of a ship. All of these terms share a common theme of smooth and efficient movement through a medium, whether it is air or water.