Speed

1. Physics The rate or a measure of the rate of motion, especially:
   1. Distance traveled divided by the time of travel.
   2. The limit of this quotient as the time of travel becomes vanishingly small; the first derivative of distance with respect to time.
   3. The magnitude of a velocity.
2. Swiftness of action.
3. 1. The act of moving rapidly.
   2. The state of being in rapid motion; rapidity.
4. A transmission gear or set of gears in a motor vehicle.
5. 1. A numerical expression of the sensitivity of a photographic film, plate, or paper to light.
   2. The capacity of a lens to accumulate light at an appropriate aperture.
   3. The length of time required or permitted for a camera shutter to open and admit light.
6. Slang A stimulant drug, especially amphetamine or methamphetamine.
7. Slang One that suits or appeals to a person's inclinations, skills, or character: Living in a large city is not my speed.
8. Archaic Prosperity; luck.