What do you mean by streamlined?

Hint: This is a special body shape designed to move smoothly in fluid such as air and water without any obstruction in the movement. Many animals have this body shape. This special body design is able to generate sudden thrust and acceleration. It provides minimum resistance when the object moves in fluid. Thus, making the motion of the objects smooth and easier.

Complete answer:
The shape of many objects moving through air or water is designed in such a way that friction can be reduced in water or air. This shape of the body is called the streamlined body. Drag is a force that makes the motion of the object slower. It occurs when fluid comes in contact with the object, the fluid exerts a force that opposes the motion of the object. Friction drag is like two bodies rubbing against each other. To reduce this drag, streamlined bodies were designed. It was designed to offer less resistance by having sleek, graceful lines on the body that could help them move smoothly. The streamline is a shape that is wide at the centre and narrows down towards the direction of the periphery.

Note:
Aquatic organisms have a streamlined-shaped body that helps them to move freely in water. Fishes have streamlined bodies which provide less resistance and help them to swim in water without any obstruction. Snakes have streamlined bodies which helps them move their body forward. Birds have a streamlined body which helps them fly smoothly in air. The same principle works with airplanes. Many machines such as airplanes and submarines have streamlined bodies to reduce friction so that they can move smoothly without any obstruction.