[ uhl-truh-fil-ter ]
/ ˌʌl trəˈfɪl tər /


Physical Chemistry. a filter for purifying sols, having a membrane with pores sufficiently small to prevent the passage of the suspended particles.
Mathematics. a filter in a topological space, having the property that no other filter exists in the space having among its subsets all the subsets in the given filter.

verb (used with object)

Physical Chemistry. to purify by means of an ultrafilter.

Nearby words

  1. ultracrepidarian,
  2. ultracritical,
  3. ultradian,
  4. ultrafast,
  5. ultrafiche,
  6. ultrafiltrate,
  7. ultrafiltration,
  8. ultrahigh,
  9. ultrahigh frequency,
  10. ultraism

Origin of ultrafilter

Related formsul·tra·fil·tra·tion [uhl-truh-fil-trey-shuh n] /ˌʌl trə fɪlˈtreɪ ʃən/, noun

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for ultra filtration

ultra filtration


engineering filtration that removes particles less than 10 microns (10 –6 m) in diameter


/ (ˌʌltrəˈfɪltə) /


a filter with small pores used to separate very small particles from a suspension or colloidal solution
Derived Formsultrafiltration (ˌʌltrəfɪlˈtreɪʃən), noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012