1.Definition: a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression

Related Noun(s):amphetamine, upper

Category: Objects

2.Definition: a rate (usually rapid) at which something happens

"The project advanced with gratifying speed"

Related Noun(s):fastness, swiftness

Category: General

3.Definition: changing location rapidly

Category: General

4.Definition: distance travelled per unit time

Related Noun(s):velocity

Category: General

5.Definition: the ratio of the focal length to the diameter of a (camera) lens system

Category: General