The Collaborative International Dictionary of English v.0.48:

Rondle \Ron"dle\, n. [Cf. Rondel.]
   1. A rondeau. [Obs.] --Spenser.
      [1913 Webster]

   2. A round mass, plate, or disk; especially (Metal.), the
      crust or scale which forms upon the surface of molten
      metal in the crucible.
      [1913 Webster]