Source : Webster's Revised Unabridged Dictionary (1913)

Necessarily \Nec"es*sa*ri*ly\, adv.
   In a necessary manner; by necessity; unavoidably;
   indispensably.

Source : WordNet®

necessarily
     adv 1: in an essential manner; "such expenses are necessarily
            incurred" [syn: {needfully}] [ant: {unnecessarily}]
     2: in such a manner as could not be otherwise; "it is
        necessarily so"; "we must needs by objective" [syn: {inevitably},
         {of necessity}, {needs}]
     3: as a highly likely consequence; "we are necessarily bound
        for federalism in Europe"