As an abbreviation for the noun quotation, quote is an informal coinage (neologism) that should not appear in serious writing: "This is a quotation (not quote) from the Bible." As a verb, quote means "to copy or repeat the words of someone else," "to cite," "to refer to for illustration": "In my talk, I expect to quote from the Bible, the Koran, and other religious works." Cite is often a more appropriate word than quote, especially when no specific reference is intended. In the expression "quote and unquote," reference is to quotation marks. The phrase is often used by a speaker to mark the beginning and ending of a quotation. This expression is acceptable in speech but not in writing.
Dictionary of problem words and expressions. Harry Shaw. 1975.