From dis- + interest.

• (British) IPA: /dɪsˈɪntɹɛst/

disinterest (uncountable)

1. An absence of interest (attention or curiosity). [from 19th c.]

   Synonyms: apathy, indifference, uninterest

   She eyed him over her martini with cool disinterest.

   • 1948, Andrew Caldecott, chapter 2, in Fires Burn Blue‎:

     […] there was no neighbourliness, worth the word, between what the postmistress called ‘our old people’ and ‘that new set’. Polite calls paid by the former on the latter were as politely returned; but at that it ended. The gulf of mutual disinterest was unbridged.

2. The absence of interest (bias or stake). [from 17th c.]

   Synonyms: impartiality

   • 2012, Christopher Clark, The Sleepwalkers, Penguin, published 2013, page 125:

     He maintained a posture of scrupulous disinterest in Balkan affairs […]

3. (obsolete) What is contrary to interest or advantage. [17th]

   Synonyms: disadvantage

   • 1676, Joseph Glanvill, Essays on Several Important Subjects in Philosophy and Religion, London: John Baker and Henry Mortlock, Essay 2 “Of Scepticism and Certainty,” p. 45,

     Now the progress of Knowledg being stopt by extreme Confidence on the one hand, and Diffidence on the other; I think that both are necessary, though perhaps one is more seasonable: For to believe that every thing is certain, is as great a disinterest to Science, as to conceive that nothing is so:

• French: désintérêt
• German: Desinteresse
• Spanish: desinterés

disinterest (disinterests, present participle disinteresting; simple past and past participle disinterested)

1. (transitive) To render disinterested.

• Portuguese: desinteressar

disinterest

1. (obsolete) Free of personal bias.

   Synonyms: disinterested

   • 1653, Jeremy Taylor, Eniautos: A Course of Sermons for all the Sundaies of the Year‎, London: Richard Royston, Sermon 23, Part 2, p. 300:

     […] if they [weaker people] can be rul’d by an understanding without, when they have none within, they shall receive this advantage, that their owne passions shall not transport their mindes, and the divisions and weaknesse of their owne sense and notices shall not make them uncertaine, and indeterminate; and the measures they shall walke by, shall be disinterest and even, and dispassionate, and full of observation.