Prime a.
 1. First in order of time; original; primeval; primitive; primary. “Prime forests.”
    She was not the prime cause, but I myself.   --Milton.
 Note: ☞ In this sense the word is nearly superseded by primitive, except in the phrase prime cost.
 2. First in rank, degree, dignity, authority, or importance; as, prime minister. “Prime virtues.”
 3. First in excellence; of highest quality; as, prime wheat; a prime quality of cloth.
 4. Early; blooming; being in the first stage. [Poetic]
 His starry helm, unbuckled, showed him prime
 In manhood where youth ended.   --Milton.
 5. Lecherous; lustful; lewd. [Obs.]
 6. Marked or distinguished by a mark (´) called a prime mark.
 Note: In this dictionary the same typographic mark is used to indicate a weak accent in headwords, and minutes of a degree in angle measurements.
 7. Math. (a) Divisible by no number except itself or unity; as, 7 is a prime number. (b) Having no common factor; -- used with to; as, 12 is prime to 25.
 Prime and ultimate ratio. Math.. See Ultimate.
 Prime conductor. Elec. See under Conductor.
 Prime factor Arith., a factor which is a prime number.
 Prime figure Geom., a figure which can not be divided into any other figure more simple than itself, as a triangle, a pyramid, etc.
 Prime meridian Astron., the meridian from which longitude is reckoned, as the meridian of Greenwich or Washington.
 Prime minister, the responsible head of a ministry or executive government; applied particularly to that of England.
 Prime mover. Mech. (a) A natural agency applied by man to the production of power. Especially: Muscular force; the weight and motion of fluids, as water and air; heat obtained by chemical combination, and applied to produce changes in the volume and pressure of steam, air, or other fluids; and electricity, obtained by chemical action, and applied to produce alternation of magnetic force. (b) An engine, or machine, the object of which is to receive and modify force and motion as supplied by some natural source, and apply them to drive other machines; as a water wheel, a water-pressure engine, a steam engine, a hot-air engine, etc. (c) Fig.: The original or the most effective force in any undertaking or work; as, Clarkson was the prime mover in English antislavery agitation.
 Prime number Arith., a number which is exactly divisible by no number except itself or unity, as 5, 7, 11.
 Prime vertical Astron., the vertical circle which passes through the east and west points of the horizon.
 Prime-vertical dial, a dial in which the shadow is projected on the plane of the prime vertical.
 Prime-vertical transit instrument, a transit instrument the telescope of which revolves in the plane of the prime vertical, -- used for observing the transit of stars over this circle.