| airspeed | (noun) the speed of an aircraft relative to the air in which it is flying | - |
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| groundspeed | (noun) the speed of an aircraft relative to the ground | - |
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| speed | (noun) changing location rapidly | Synonyms: hurrying, speeding |
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| (noun) a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression | Synonyms: amphetamine, pep pill, upper |
| (noun) a rate (usually rapid) at which something happens | Synonyms: fastness, swiftness |
| (noun) the ratio of the focal length to the diameter of a (camera) lens system | Synonyms: f number, focal ratio, stop number |
| (noun) distance travelled per unit time | Synonyms: velocity |