Date: circa 1612
a. not having the mind or feelings engaged ; not interested <telling them in a disinterested voice — Tom Wicker> <disinterested in women — J. A. Brussel> b. no longer interested <husband and wife become disinterested in each other — T. I. Rubin> 2. free from selfish motive or interest ; unbiased <a disinterested decision> < Synonyms: see indifferent • disinterestedly adverb Usage: Disinterested and uninterested have a tangled history. Uninterested originally meant impartial, but this sense fell into disuse during the 18th century. About the same time the original sense of disinterested also disappeared, with uninterested developing a new sense—the present meaning—to take its place. The original sense of uninterested is still out of use, but the original sense of disinterested revived in the early 20th century. The revival has since been under frequent attack as an illiteracy and a blurring or loss of a useful distinction. Actual usage shows otherwise. Sense 2 of disinterested is still its most frequent sense, especially in edited prose; it shows no sign of vanishing. A careful writer may choose sense 1a of disinterested in preference to uninterested for emphasis <. Further, disinterested has developed a sense (1b), perhaps influenced by sense 1 of the prefix dis-, that contrasts with uninterested <. Still, use of senses 1a and 1b will incur the disapproval of some who may not fully appreciate the history of this word or the subtleties of its present use.
New Collegiate Dictionary. 2001.