The Collaborative International Dictionary of English v.0.48:

Circumference \Cir*cum"fer*ence\, n. [L. circumferentia.]
   [1913 Webster]
   1. The line that goes round or encompasses a circular figure;
      a periphery. --Millon.
      [1913 Webster]

   2. A circle; anything circular.
      [1913 Webster]

            His ponderous shield . . .
            Behind him cast. The broad circumference
            Hung on his shoulders like the moon.  --Milton.
      [1913 Webster]

   3. The external surface of a sphere, or of any orbicular
      body.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Circumference \Cir*cum"fer*ence\, v. t.
   To include in a circular space; to bound. [Obs.] --Sir T.
   Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

circumference
    n 1: the size of something as given by the distance around it
         [syn: circumference, perimeter]
    2: the boundary line encompassing an area or object; "he had
       walked the full circumference of his land"; "a danger to all
       races over the whole circumference of the globe" [syn:
       circumference, circuit]
    3: the length of the closed curve of a circle