The term 'BIG MONKEY' can be broken down into two crossword solutions: APE (3 letters) and BABOON (6 letters). APE is a common name for any primate of the superfamily Hominoidea, which includes humans, gorillas, chimpanzees, and orangutans. Baboons are large, terrestrial Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. They are found in Africa and the Arabian Peninsula. Both apes and baboons are considered to be big monkeys, and they are both highly intelligent primates.