A query for a definition. A dictionary lookup is a much less sophisticated function than a general search for words in an article. Dictionary lookups use a single index of pointers to the terms in a database, and the index is quickly scanned to find a match. A general search requires a much more sophisticated matching process because there may be words in the query that must appear in the result, but not necessarily together, and there may be words that have to be together. For example, in a Google search for
"rugged Android smartphone" -Samsung, three words must be together and "Samsung" must not be in the resulting article (the -Samsung means "not Samsung"). See
right-click dictionary lookup.