Ignored words(noise words) are words such as:a, as, etc
you could check them( add/remove) in the default installation path:
C:\Program Files\Common Files\System\MSSearch\Data\Config
You also may encounter Error 7619, "The query contained only ignored words" when using any of the full-text predicates in a full-text query, such as CONTAINS(pr_info, 'between AND king'). The word "between" is an ignored or noise word and the full-text query parser considers this an error, even with an OR clause. Consider rewriting this query to a phrase-based query, removing the noise word, or options offered in Knowledge Base article Q246800, "INF: Correctly Parsing Quotation Marks in FTS Queries". Also, consider using Windows 2000 Server: there have been some enhancements to the word-breaker files for Indexing Services.