ultrafilter

Short definition from Wiktionary

Noun

1. 1
   A device that performs ultrafiltration.
2. 2
   A proper filter which has a law of dichotomy for complements.
3. 3
   A filter (subset of a poset) that is maximal as a set with respect to the definition of proper filter.

Verb

1. 1
   To filter by ultrafiltration.