When I check the status of Windows Update on my laptop running Win10 x64, it says that updates are available, and that the download is at 98% complete. When I click on details, I can see that KB3105210 is waiting for installation, KB3106932 is waiting for installation, and KB2267602 (definition update for Windows Defender to 1.209.1525.0) is waiting for download. The definition update never downloads, and rebooting the machine makes no difference - the status of these three updates doesn't change.

When I open Windows Defender, I can see that it is running definitions version 1.209.1996.0, created and installed earlier this morning, which makes it seem that the definition that Windows Update is trying to download is an old one that is no longer available. How can I do a reset on Windows Update so that it is no longer trying to get this old definition update?