vehicle

noun

• 1a thing used for transporting people or goods, especially on land, such as a car, truck, or cart.

• 2a thing used to express, embody, or fulfill something:I use paint as a vehicle for my ideas
• a substance that facilitates the use of a drug, pigment, or other material mixed with it.
• the figurative language used in a metaphor, as distinct from the metaphor’s subject. Often contrasted with tenor² (sense 1).
• a movie, television program, song, etc., that is intended to display the leading performer to the best advantage.