NOUN (3)

1. the body of Jews (or Jewish communities) outside Palestine or modern Israel;

2. the dispersion of the Jews outside Israel; from the destruction of the temple in Jerusalem in 587-86 BC when they were exiled to Babylonia up to the present time;

3. the dispersion or spreading of something that was originally localized (as a people or language or culture);

The Collaborative International Dictionary of English v.0.48:

Diaspora \Di*as"po*ra\, n. [Gr. ?. See Diaspore.]
   Lit., "Dispersion." -- applied collectively: (a) To those
   Jews who, after the Exile, were scattered through the Old
   World, and afterwards to Jewish Christians living among
   heathen. Cf. --James i. 1. (b) By extension, to Christians
   isolated from their own communion, as among the Moravians to
   those living, usually as missionaries, outside of the parent
   congregation.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

diaspora
    n 1: the body of Jews (or Jewish communities) outside Palestine
         or modern Israel
    2: the dispersion of the Jews outside Israel; from the
       destruction of the temple in Jerusalem in 587-86 BC when they
       were exiled to Babylonia up to the present time
    3: the dispersion or spreading of something that was originally
       localized (as a people or language or culture)