"Apocryphal" refers to sayings or works that are not authentic, or have doubtful authenticity. The adjective is often used in reference to quotes or references that are supposedly from the Bible, but for which there is broad consensus that authenticity is lacking.
A common example is when people cite the apocryphal Adulteress Story, typically to make a liberal argument.
Entire books that are considered to be apocryphal with respect to the Bible are called the "Apocrypha".