A line that is tangent to the velocity of flow of a fluid; equivalent to the path of a specific particle in that flow.
"The engineer marked a streamline on the diagram to show exactly how each water molecule traveled through the curved pipe."
contour economically or efficiently
"The manager decided to streamline the office layout by removing unnecessary furniture and rearranging desks to maximize space usage."
To design and construct the contours of a vehicle etc. so as to offer the least resistance to its flow through a fluid.
"The engineer streamlined the submarine's hull to reduce drag as it moved through the ocean."