Definitions
1.nounA line that is tangent to the velocity of flow of a fluid; equivalent to the path of a specific particle in that flow.
2.nounOn a weather chart, a line that is tangent to the flow of the wind.
3.verbTo design and construct the contours of a vehicle etc. so as to offer the least resistance to its flow through a fluid.
4.verb(by extension) To simplify or organize a process in order to increase its efficiency.
5.verbTo modernise.