NCR (no country redirect) is a Google search parameter that tells the search engine to show results for the country specified in the URL rather than redirecting to the country from which the search is being conducted.
When you go to Google.com, Google automatically detects your location and then redirects their URL to the one for your country. If you live in the United Kingdom, for example, Google.com resolves to Google.co.uk. Google search engine results pages (SERP) for various countries can be quite different because they display pages from the user's country more prominently. That behavior might be useful for someone looking for a nearby location, business or product but is less helpful for other types of searches, such as research, for which relevance to the search query is often the most important criteria.
To ensure that Google returns results from the .com domain rather than one specific to a non-U.S. country, type a forward slash (/) and the letters ncr after the URL. Marketers and website owners can also use NCR to monitor page ranking in various countries. To do that, add /ncr to the Google URL for the country in question.
See a video demonstration of using NCR to stop Google from redirecting to the user's country: