Many object to the use of disinterested to mean “not interested, indifferent.” They insist that disinterested can mean only “impartial”: A disinterested observer is the best judge of behavior. However, both senses are well established in all varieties of English, and the sense intended is almost always clear from the context.
Examples from the Web for disinterestedly
Madame Guyon taught that it was possible to love God for himself alone, purely and disinterestedly.Classic French Course in English|William Cleaver Wilkinson
Lucius respects my father too much for that—and too disinterestedly.The Lion's Brood|Duffield Osborne
She cannot comprehend why, being a beautiful and distinguished woman, she has nobody who cares for her disinterestedly.Csar or Nothing|Po Baroja Baroja
Dick spent most of the day watching the contests, as disinterestedly as if he was a native of the Isle of Java.At Start and Finish|William Lindsey
As for the accuracy of the opinions so disinterestedly upheld, I neither combat nor assent to them.Ralph Wilton's weird|Mrs. Alexander
British Dictionary definitions for disinterestedly
Word Origin and History for disinterestedly
1610s, "unconcerned," the sense we now would ascribe to uninterested, with the sense of "impartial" going to disinteressed (c.1600). See dis- + interest. Modern sense of disinterested is first attested 1650s. As things now stand, disinterested means "free from personal bias," while uninterested means "caring nothing for the matter in question." Related: Disinterestedly; disinterestedness.