The Collaborative International Dictionary of English v.0.48:

Parboil \Par"boil`\, v. t. [imp. & p. p. Parboiled; p. pr. &
   vb. n. Parboiling.] [OE. parboilen, OF. parbouillir to cook
   well; par through (see Par) + bouillir to boil, L. bullire.
   The sense has been influenced by E. part. See 1st Boil.]
   1. To boil or cook thoroughly. [Obs.] --B. Jonson.
      [1913 Webster]

   2. To boil in part; to cook partially by boiling.
      [1913 Webster]

   3. Hence: (Fig.) To do (something) only part way, or
      incompletely. Also used intransitively.
      [PJC]