Yes, user can stop the in progress search.

Steps to follow - 

  1. When your search is in progress, the Stop search button will appear. 
  2. Clicking this Stop search button will stop the in progress search.
  3. On stopping the search user will see a warning message on the screen.
  4. When the search is stopped user will see a success message on the screen.


PS: View Metadata Search, Salesforce quick search app on Salesforce AppExchange: https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000009wgF7EAI