The Collaborative International Dictionary of English v.0.48:

Providential \Prov`i*den"tial\, a. [Cf. F. providentiel.]
   Effected by, or referable to, divine direction or
   superintendence; as, the providential contrivance of thing; a
   providential escape. -- Prov"i*den"tial*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

providential
    adj 1: peculiarly fortunate or appropriate; as if by divine
           intervention; "a heaven-sent rain saved the crops"; "a
           providential recovery" [syn: heaven-sent,
           providential, miraculous]
    2: relating to or characteristic of providence; "assumption that
       nature operates only according to a providential plan"-
       M.R.Cohen
    3: resulting from divine providence; "providential care"; "a
       providential visitation" [syn: providential, divine]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "providential":
   God-given, accorded, allowed, anticipant, anticipatory,
   appropriate, auspicious, befitting, benignant, bestowed, blessed,
   blessed with luck, clairvoyant, convenient, divinatory, expedient,
   farseeing, farsighted, favorable, favored, felicitous, fit,
   fitting, forehanded, foreknowing, foreseeing, foresighted,
   forethoughted, forethoughtful, fortunate, given, granted,
   gratuitous, happy, in luck, intuitive, kind, kindly, longsighted,
   lucky, meet, opportune, precognitive, precognizant, prepared,
   prescient, propitious, provident, prudent, ready, ripe, sagacious,
   seasonable, sortable, suitable, timely, vouchsafed, well,
   well-timed



The Devil's Dictionary (1881-1906):

PROVIDENTIAL, adj.  Unexpectedly and conspicuously beneficial to the
person so describing it.