Enter a clue or pattern or both:
The Clue
Reference book (12 letter answer)
The Answer
ENCYCLOPEDIA
Tags
Notes
The answer ENCYCLOPEDIA is so rare that it appears less than once every 2500 puzzles.
Definition
ENCYCLOPEDIA as a noun:
1. (encyclopedia, cyclopedia, encyclopaedia, cyclopaedia) = a reference work (often in several volumes) containing articles on various topics (often arranged in alphabetical order) dealing with the entire range of human knowledge or with some particular specialty