The Collaborative International Dictionary of English v.0.48:

Momentarily \Mo"men*ta*ri*ly\, adv.
   1. Every moment; from moment to moment. --Shenstone.
      [1913 Webster]

   2. In a moment; in the immediate future.
      [PJC]

WordNet (r) 3.0 (2006):

momentarily
    adv 1: for an instant or moment; "we paused momentarily before
           proceeding"; "a cardinal perched momently on the dogwood
           branch" [syn: momentarily, momently]
    2: at any moment; "she will be with you momently" [syn:
       momentarily, momently]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "momentarily":
   briefly, fleetingly, flickeringly, flittingly, for a moment,
   immediately, in an instant, instantaneously, instanter, instantly,
   just now, just then, momentaneously, momently, on the dot,
   on the instant, on the nail, on the spot, quickly, shortly,
   swiftly, transiently