The following 3 entries include the term cui.
: a principle that probable responsibility for an act or event lies with one having something to gain
cui in vitanoun
: a writ of entry by means of which a widow sought to recover lands which had belonged to her but had been transferred by her husband during his lifetime
: an endangered sucker (Chasmistes cujus) of the family Catostomidae that is found only in Pyramid lake and the Truckee river, Nevada