Definition of "streamline"

(physics) A line that is tangent to the velocity of flow of a fluid; equivalent to the path of a specific particle in that flow.  examples

(meteorology) On a weather chart, a line that is tangent to the flow of the wind.

(transitive) To design and construct the contours of a vehicle etc. so as to offer the least resistance to its flow through a fluid.  examples

(transitive, by extension) To simplify or organize a process in order to increase its efficiency.  examples

(transitive) To modernise.  examples