Definitions for "Filter Words"
Words such as of, is, am, were, was, the, for, do, ETC, that search engines deem irrelevant for indexing purposes.
Edit / world wide web search engine term for the little words that are discarded or ignored when doing queries and adding web sites to their databases. These include such words as "the", "to", "is", "an", "of", "for", etc.
This term is often confused with Stop Words. Filter words are common words that search engines remove from web pages before adding them to their databases. These include words along the lines of (the,is,an,of,for,do). As you can imagine, removing these words can save search engines enormous amounts of database space.