4. focal ratio, f number, stop number, speed -- (the ratio of the focal length to the diameter of a (camera) lens system)
5. amphetamine, pep pill, upper, speed -- (a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression)
Overview of verb speed
The verb speed has 5 senses (first 5 from tagged texts)
1. (7) rush, hotfoot, hasten, hie, speed, race, pelt along, rush along, cannonball along, bucket along, belt along -- (step on it; "He rushed down the hall to receive his guests"; "The cars raced down the street")
2. (5) accelerate, speed up, speed, quicken -- (move faster; "The car accelerated")
3. (3) speed -- (travel at an excessive or illegal velocity; "I got a ticket for speeding")
4. (3) travel rapidly, speed, hurry, zip -- (move very fast; "The runner zipped past us at breakneck speed")
5. (1) accelerate, speed, speed up -- (cause to move faster; "He accelerated the car")