noun

• (obsolete) What is contrary to interest or advantage.
  "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:"

verb

• (transitive) To render disinterested.
  "The Moscow Bolsheviks may disinterest themselves in the fate of Ukrainian or White Russian territories under Polish rule; but nationalist States in the Ukraine or White Russia could never evince such indifference."

adj

• (obsolete) Free of personal bias.
  "[…] 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."