The Collaborative International Dictionary of English v.0.48:

Overtop \O`ver*top"\, v. t. [imp. & p. p. Overtopped; p. pr. &
   vb. n. Overtopping.]
   1. To rise above the top of; to exceed in height; to tower
      above. "To o'ertop old Pelion." --Shak.
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   2. To go beyond; to transcend; to transgress.
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            If kings presume to overtop the law by which they
            reign, . . . they are by law to be reduced into
            order.                                --Milton.
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   3. To make of less importance, or throw into the background,
      by superior excellence; to dwarf; to obscure. --Becon.
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