The Collaborative International Dictionary of English v.0.48:

Circlet \Cir"clet\, n.
   1. A little circle; esp., an ornament for the person, having
      the form of a circle; that which encircles, as a ring, a
      bracelet, or a headband.
      [1913 Webster]

            Her fair locks in circlet be enrolled. --Spenser.
      [1913 Webster]

   2. A round body; an orb. --Pope.
      [1913 Webster]

            Fairest of stars . . . that crown'st the smiling
            morn
            With thy bright circlet.              --Milton.
      [1913 Webster]

   3. A circular piece of wood put under a dish at table. [Prov.
      Eng.] --Halliwell.
      [1913 Webster]

WordNet (r) 3.0 (2006):

circlet
    n 1: a small circle
    2: decorated metal band worn around the head