The Collaborative International Dictionary of English v.0.48:

Supplicate \Sup"pli*cate\, v. t. [imp. & p. p. Supplicated; p.
   pr. & vb. n. Supplicating.] [L. supplicatus, p. p. of
   supplicare to supplicate; of uncertain origin, cf. supplex,
   supplicis, humbly begging or entreating; perhaps fr. sub
   under + a word akin to placare to reconcile, appease (cf.
   Placable), or fr. sub under + plicare to fold, whence the
   idea of bending the knees (cf. Ply, v. t.). Cf. Supple.]
   1. To entreat for; to seek by earnest prayer; to ask for
      earnestly and humbly; as, to supplicate blessings on
      Christian efforts to spread the gospel.
      [1913 Webster]

   2. To address in prayer; to entreat as a supplicant; as, to
      supplicate the Deity.
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   Syn: To beseech; entreat; beg; petition; implore; importune;
        solicit; crave. See Beseech.
        [1913 Webster]