The Collaborative International Dictionary of English v.0.48:

Peak \Peak\, v. i. [imp. & p. p. Peaked (p[=e]kt); p. pr. &
   vb. n. Peaking.]
   1. To rise or extend into a peak or point; to form, or appear
      as, a peak.
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            There peaketh up a mighty high mount. --Holand.
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   2. Hence: To achieve a maximum of numerical value, intensity
      of activity, popularity, or other characteristic, followed
      by a decline; as, the stock market peaked in January; his
      performance as a pitcher peaked in 1990; sales of the XTX
      model peaked at 20,000 per year.
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   3. To acquire sharpness of figure or features; hence, to look
      thin or sickly. "Dwindle, peak, and pine." --Shak.
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   4. [Cf. Peek.] To pry; to peep slyly. [archaic] --Shak.
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   Peak arch (Arch.), a pointed or Gothic arch.
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