The Collaborative International Dictionary of English v.0.48:

Edgeways \Edge"ways\, Edgewise \Edge"wise\, adv.
   With the edge towards anything; in the direction of the edge.
   [1913 Webster]

   to get a word in edgewise to succeed in expressing an
      opinion in a conversation, in spite of constant speech
      from another or others; as, he talked incessantly and I
      couldn't get a word in edgewise.

   Note: the form edgeways is now uncommon.
         [PJC]

               Glad to get in a word, as they say, edgeways.
                                                  --Sir W.
                                                  Scott.
         [1913 Webster]

WordNet (r) 3.0 (2006):

edgewise
    adv 1: with the edge forward or on, by, or toward the edge; "he
           sawed the board edgeways"; "held it edgewise" [syn:
           edgeways, edgewise]
    2: as if by an edge; barely; "I could not get a word in
       edgewise" [syn: edgewise, edgeways]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "edgewise":
   aside, askance, askant, asquint, broadside, broadside on, crabwise,
   edgeway, edgeways, glancingly, laterad, laterally, on its side,
   on the beam, right and left, sideling, sidelong, sideward,
   sidewards, sideway, sideways, sidewise, sidling