WordNet (r) 3.0 (2006):

swung dash
    n 1: a punctuation mark used in text to indicate the omission of
         a word

The Free On-line Dictionary of Computing (30 December 2018):

swung dash

    A character similar to tilde but appearing
   in the same vertical position as a dash, i.e. half way up
   rather than at the top like tilde.  ASCII does not include a
   swung dash so tilde is used instead.

   It is commonly used for "approximates" or "is approximately
   equal to".

   (1997-06-28)