The Collaborative International Dictionary of English v.0.48:

Granny \Gran"ny\, n.
   A grandmother; a grandam; familiarly, an old woman.
   [1913 Webster]

   Granny's bend, or Granny's knot (Naut.), a kind of
      insecure knot or hitch; a reef knot crossed the wrong way.
      [1913 Webster]

WordNet (r) 3.0 (2006):

granny
    n 1: the mother of your father or mother [syn: grandma,
         grandmother, granny, grannie, gran, nan, nanna]
    2: an old woman
    3: a reef knot crossed the wrong way and therefore insecure
       [syn: granny knot, granny]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "granny":
   Methuselah, antediluvian, antique, back number, beldam,
   conservative, crone, dad, dame, dodo, dowager, elder, fogy, fossil,
   frump, fud, fuddy-duddy, fuss, fuss-budget, fusser, fusspot,
   gammer, grandam, grandma, grandmother, grannam, great-grandmother,
   hag, has-been, longhair, matriarch, mid-Victorian, mossback,
   old battle-ax, old believer, old crock, old dame, old dodo,
   old fogy, old girl, old granny, old lady, old liner, old maid,
   old man, old poop, old trot, old wife, old woman, old-timer,
   patriarch, pop, pops, reactionary, regular old fogy, relic, square,
   starets, traditionalist, trot, war-horse, witch