insensibly

from WordNet (r) 3.0 (2006)

insensibly
    adv 1: in a numb manner; without feeling; "I stared at him
           numbly" [syn: {numbly}, {insensibly}]

from The Collaborative International Dictionary of English v.0.48

Insensibly \In*sen"si*bly\, adv.
   In a manner not to be felt or perceived; imperceptibly;
   gradually.
   [1913 Webster]

         The hills rise insensibly.               --Addison.
   [1913 Webster]