The Collaborative International Dictionary of English v.0.48:

dignitary \dig"ni*ta*ry\, n.; pl. dignitaries. [Cf. F.
   dignitaire, fr. L. dignitas.]
   One who possesses exalted rank or holds a position of dignity
   or honor; especially, one who holds an ecclesiastical rank
   above that of a parochial priest or clergyman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dignitary
    n 1: an important or influential (and often overbearing) person
         [syn: very important person, VIP, high-up,
         dignitary, panjandrum, high muckamuck]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "dignitary":
   Establishment, VIP, baron, big cheese, big gun, big man, big name,
   big noise, big shot, big wheel, bigwig, brass, brass hat,
   celebrity, chief, dignity, elder, eminence, fat cat, father,
   figure, great man, high-muck-a-muck, higher-up, hotshot,
   important person, interests, lion, lords of creation, luminary,
   magnate, man of mark, mogul, nabob, name, notability, notable,
   official, panjandrum, person of renown, personage, personality,
   pillar of society, power, power elite, ruling circle, sachem,
   somebody, something, star, superstar, the great, the top,
   top brass, top people, tycoon, very important person, worthy