1. in a manner free from bias, prejudice, or personal interest; impartially
Usage: most common modern sense
2. in a manner showing lack of interest or concern; indifferently
Usage: less common; sometimes considered nonstandard by prescriptivists who reserve 'disinterested' for sense 1

Examples

• The judge ruled disinterestedly on the case, setting aside her personal feelings.
• A disinterestedly chosen panel of experts reviewed the research proposal.
• He listened disinterestedly to the presentation, showing no enthusiasm.
• The mediator approached the dispute disinterestedly, favoring neither party.
• She observed the debate disinterestedly, unwilling to take sides.
• The committee members voted disinterestedly, based solely on merit.
• He responded disinterestedly to the news, as if it did not concern him.