Definitions of Boolean search on the Web:

• Boolean algebra, developed in 1854 by George Boole in his book An Investigation of the Laws of Thought, is a variant of ordinary algebra as taught ...
  en.wikipedia.org/wiki/Boolean_search

• A search formed by joining simple terms with AND, OR and NOT for the purpose of limiting or qualifying the search. ...
  www.virtechseo.com/seoglossary.htm

• a search using Boolean operators
  www.foodinfoquest.com/glossary

• A method of searching for information in databases that combines search terms with the operators AND, OR, NOT, and parentheses.
  www.bigbaer.com/reference/glossary.internet.html

• An information search that uses the words “and,” “or,” “not” to focus a search. “And” narrows a search by requiring all key words to be present in the retrieved records. “Or” broadens a search, retrieving records with one, two, or all of the key words. ...
  www.bu.edu/showme/glossary/glossary.html

• A means of narrowing an automated search through logical operators such as "and", "or" and "not".
  archeion-aao.fis.utoronto.ca/glossary.html

• This is a type of search that allows you to exclude or include certain words or phrases using words such as AND, NOT, and OR.
  www.corporatewebsitemarketing.com/search-engine-marketing-glossary.html

• A search which uses "and" , "or", or "not" to link words or phrases. Examples are "russia AND religion", "dostoyevski OR dostoevski", "russian music NOT jazz".
  www2.lv.psu.edu/library/guides/Thea105/glossary.html

• A Boolean search involves searching with words like AND, OR, NOT. Using these words and other similar words can help you get more specific results. ...
  www.kidzworld.com/article/4079-advanced-search-engine-lingo