You can search for keywords, or known CWE-IDs, or even a general term in the search box. This will find all matching pages to that term on the CWE web site, as all web pages are indexed.
To limit your search to only individual CWE entry pages, include "inurl:definitions" in your query
Let’s say you want to find a weakness related to Cross-Site Scripting (XSS) to map a CVE Record that deals with XSS. Here is the process you could follow to get to that information using the search feature.
Search for “xss” returns the following:Keyword Search - XSS