clearance
    n 1: the distance by which one thing clears another; the space
         between them
    2: vertical space available to allow easy passage under
       something [syn: headroom, headway, clearance]
    3: permission to proceed; "the plane was given clearance to
       land"

Clearance \Clear"ance\ (kl[=e]r"ans), n.
   1. The act of clearing; as, to make a thorough clearance.
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   2. A certificate that a ship or vessel has been cleared at
      the customhouse; permission to sail.
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            Every ship was subject to seizure for want of
            stamped clearances.                   --Durke
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   3. Clear or net profit. --Trollope.
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   4. (Mach.) The distance by which one object clears another,
      as the distance between the piston and cylinder head at
      the end of a stroke in a steam engine, or the least
      distance between the point of a cogwheel tooth and the
      bottom of a space between teeth of a wheel with which it
      engages.
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   Clearance space (Steam engine), the space inclosed in one
      end of the cylinder, between the valve or valves and the
      piston, at the beginning of a stroke; waste room. It
      includes the space caused by the piston's clearance and
      the space in ports, passageways, etc. Its volume is often
      expressed as a certain proportion of the volume swept by
      the piston in a single stroke.
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CLEARANCE, com. law. The name of a certificate given by the collector of a 
port, in which is stated the master or commander (naming him) of a ship or 
vessel named and described, bound for a port, named, and having on board 
goods described, has entered and cleared his ship or vessel according to 
law. 
     2. The Act of Congress of 2d March, 1790, section 93, directs, that the 
master of any vessel bound to a foreign place, shall deliver to the 
collector of the [dis ot?] from which such vessel shall be about to depart, a

manifest of all the cargo on board, and the value thereof, by him 
subscribed, and shall swear or affirm to the truth thereof; whereupon the 
collector shall grant a clearance for such vessel and her cargo; but without 
specifying the particulars thereof in such clearance, unless required by the 
master so to do. And if any vessel bound to any foreign place shall depart 
on her voyage to such foreign place, without delivering such a manifest and 
obtaining a clearance, the master shall forfeit and pay the sum of five 
hundred dollars for every such offence. Provided, anything to the contrary 
notwithstanding, the collectors and other officers of the customs shall pay 
due regard to the inspection laws of the states in which they respectively 
act, in such manner, that no vessel having on board goods liable to 
inspection, shall be cleared out, until the master or other person shall 
have produced such certificate, that all such goods have been duly 
inspected, as the laws of the respective states do or may require, to be 
produced to the collector or other officer of the customs. And provided, 
that receipts for the payment of all legal fees which shall have accrued on 
any vessel, shall, before any clearance is granted, be produced to the 
collector or other officer aforesaid. 
     3. According to Boulay-Paty, Dr. Com. tome 2, p. 19, the clearance is 
imperiously demanded for the safety of the vessel; for if a vessel should be 
found without it at  sea, it may be legally taken and brought  into some 
port for adjudication, on a charge  of piracy. Vide Ship's papers.