The Collaborative International Dictionary of English v.0.48:

Gaffer \Gaf"fer\ (g[a^]f"f[~e]r), n. [Possibly contr. fr.
   godfather; but prob. fr. gramfer for grandfather. Cf.
   Gammer.]
   1. An old fellow; an aged rustic.
      [1913 Webster]

            Go to each gaffer and each goody.     --Fawkes.
      [1913 Webster]

   Note: Gaffer was originally a respectful title, now
         degenerated into a term of familiarity or contempt when
         addressed to an aged man in humble life.
         [1913 Webster]

   2. A foreman or overseer of a gang of laborers. [Prov. Eng.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

gaffer
    n 1: an elderly man [syn: old-timer, oldtimer, gaffer,
         old geezer, antique]
    2: an electrician responsible for lighting on a movie or tv set
    3: a person who exercises control over workers; "if you want to
       leave early you have to ask the foreman" [syn: foreman,
       chief, gaffer, honcho, boss]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "gaffer":
   Big Brother, Father Time, Methuselah, Nestor, Old Paar, auditor,
   boatswain, boss, centenarian, chief, comptroller, controller,
   dotard, duffer, elder, floor manager, floorman, floorwalker,
   foreman, ganger, geezer, golden-ager, gramps, grandfather,
   grandsire, graybeard, head, headman, inspector, monitor,
   nonagenarian, noncommissioned officer, octogenarian, old boy,
   old chap, old codger, old dog, old duffer, old geezer, old gent,
   old gentleman, old man, old party, old-timer, older, oldster,
   overman, overseer, pantaloon, patriarch, presbyter, proctor,
   senior citizen, septuagenarian, sexagenarian, sirdar, slave driver,
   straw boss, subforeman, super, superintendent, supervisor,
   surveyor, taskmaster, the quiet-voiced elders, venerable sir,
   veteran, visitor