Artificial intelligent assistant

rarefier

ˈrarefier rare.
  [f. rarefy v. + -er1.]
  That which rarefies.

1686 Goad Celest. Bodies i. ii. 6 Such infinite variety of Rarefiers and Condensers. 1798 Hutton Course Math. (1807) II. 240 The air-pump, or rarefier.

Oxford English Dictionary

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