The Collaborative International Dictionary of English v.0.48:

Suppurate \Sup"pu*rate\, v. i. [imp. & p. p. Suppurated; p.
   pr. & vb. n. Suppurating.] [L. suppuratus, p. p. of
   suppurare to suppurate, cause to suppurate; sub under + pus,
   puris, matter. See Pus.]
   To generate pus; as, a boil or abscess suppurates.
   [1913 Webster]