Prevents Google from showing a Site Links search box.
https://support.google.com/webmasters/answer/79812
Widgets · Site Search
Get access to data on 5,882 websites that are Google No Site Links Search Customers. We know of 3,436 live websites using Google No Site Links Search and an additional 2,446 sites that used Google No Site Links Search historically and 1,538 websites in the United States.
Get a list of 5,882 websites using Google No Site Links Search which includes location information, hosting data, contact details, 3,436 currently live websites and an additional 10,494 domains that redirect to sites in this list. 2,446 sites that used this technology previously and 1,538 websites in the United States currently using Google No Site Links Search.