Sigma

from WordNet (r) 3.0 (2006)

sigma
    n 1: the 18th letter of the Greek alphabet

from The Collaborative International Dictionary of English v.0.48

Sigma \Sig"ma\, n.; pl. {Sigmas}. [L., from Gr. ???, ???.]
   The Greek letter [Sigma], [sigma], or [sigmat] (English S, or
   s). It originally had the form of the English C.
   [1913 Webster]

from The Free On-line Dictionary of Computing (8 July 2008)

SIGMA

   A scientific {visual programming} environment from NASA.

   (http://fi-www.arc.nasa.gov/fia/projects/sigma/).

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

SIGMA
       Software Industrialized Generator and Maintenance Aids system
(MITI)

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