The Collaborative International Dictionary of English v.0.48:

Usance \Us"ance\, n. [F. See Use, v. t.]
   [1913 Webster]
   1. Use; usage; employment. [Obs.] --Spenser.
      [1913 Webster]

   2. Custom; practice; usage. [Obs.] --Gower. Chaucer.
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   3. Interest paid for money; usury. [Obs.] --Shak.
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   4. (Com.) The time, fixed variously by the usage between
      different countries, when a bill of exchange is payable;
      as, a bill drawn on London at one usance, or at double
      usance.
      [1913 Webster]

WordNet (r) 3.0 (2006):

usance
    n 1: the period of time permitted by commercial usage for the
         payment of a bill of exchange (especially a foreign bill of
         exchange)
    2: (economics) the utilization of economic goods to satisfy
       needs or in manufacturing; "the consumption of energy has
       increased steadily" [syn: consumption, economic
       consumption, usance, use, use of goods and services]
    3: accepted or habitual practice [syn: custom, usage,
       usance]