the path of a fluid, e.g. air or water, relative to a solid body past which the fluid is moving smoothly without turbulence

a contour given to a car, aeroplane, etc so as to minimize resistance to motion, e.g. through air

to design or construct (a vehicle, etc) so as to minimize resistance to motion, e.g. through air with a streamline

to make (an organization) simpler or, more efficient, or better integrated