Source : Webster's Revised Unabridged Dictionary (1913)

Peak \Peak\, v. i. [imp. & p. p. {Peaked}; p. pr. & vb. n.
   {Peaking}.]
   1. To rise or extend into a peak or point; to form, or appear
      as, a peak.

            There peaketh up a mighty high mount. --Holand.

   2. To acquire sharpness of figure or features; hence, to look
      thin or sicky. ``Dwindle, peak, and pine.'' --Shak.

   3. [Cf. {Peek}.] To pry; to peep slyly. --Shak.

   {Peak arch} (Arch.), a pointed or Gothic arch.

Peaked \Peaked\, a.
   1. Pointed; ending in a point; as, a peaked roof.

   2. (Oftener ?) Sickly; not robust. [Colloq.]

Source : WordNet®

peaked
     adj 1: somewhat ill or prone to illness; "my poor ailing
            grandmother"; "feeling a bit indisposed today"; "you
            look a little peaked"; "feeling poorly"; "a sickly
            child"; "is unwell and can't come to work" [syn: {ailing},
             {indisposed}, {peaked(p)}, {poorly(p)}, {sickly}, {unwell},
             {under the weather}]
     2: having or rising to a peak; "the peaked ceiling"; "the
        island's peaked hills"