To rebuild or replenish with all new material; to restore to original (or better) working order and appearance.
To modernise.
To design and construct the contours of a vehicle etc. so as to offer the least resistance to its flow through a fluid.
To simplify or organize a process in order to increase its efficiency.
On a weather chart, a line that is tangent to the flow of the wind.
A line that is tangent to the velocity of flow of a fluid; equivalent to the path of a specific particle in that flow.