Q:

Failiure to update Windows defender virus & spyware definition - 0x8024402c

An error with error code 0x8024402c is thrown  each time while trying to update Windows Defender's virus & spyware definition.
Checked the following for diagnosis, and found no problem with these;

No pending important updates in Windows Update (automatic update option is checked)
No other antivirus installed
Windows Update Agent is up to date
No proxy server involved

What else do I have to check?  

 UPDATE
If the chosen answer below doesn't work for you, here's another solution that may work; change your DNS server IP to Google's, see how to do that here.

A:

Windows defender virus & spyware definition not updating
Run the Microsoft "Fixit" application.

When you use the Windows Update website or the Microsoft Update website to check for and install updates, you may receive one of the errors that are listed in the "Symptoms" section.
Windows 8.1, Windows 8 or Windows 7 
The Automatically diagnose and fix common problems with Windows Update
  troubleshooter may automatically fix the problem described in this
  article.

There is a link on the page to Microsoft Fixit - the run now button

...
Symptoms
When you use the Windows Update website or the Microsoft Update
  website to check for and install updates, you may receive one of the
  following error code in the error messages:
...
0x8024402C              -2145107924  WU_E_PT_WINHTTP_NAME_NOT_RESOLVED
...
Cause
These errors may be caused by any of the following issues:

Programs or processes that interfere with Internet communications
Resource issues on the computer
High Internet activity
Recoverable database errors

Source Temporary connection-related errors may occur when you use Windows Update or Microsoft Update 

Additional troubleshooting steps
If the above doesn't fix your issue, then see How to solve connection problems concerning Windows Update or Microsoft Update.

