An encyclopedia was a book or computer compilation of comprehensive references containing articles on a wide range of subjects or on numerous aspects of a particular field, usually arranged alphabetically.
While investigating a humanoid that could generate and control energy, who referred to himself as Apollo later that same year, Pavel Chekov began to spout off information on similar creatures. After naming the electric eel and giant dry-worm, he was stopped by Dr. McCoy, who told him "not the whole encyclopedia, Chekov", later quipping on Chekov's dedicated thoroughness by stating "Spock's contaminating this boy, Jim." (TOS: "Who Mourns for Adonais?")
When Spock was infected with choriocytosis in 2270, Doctor Leonard McCoy remarked that he would be sorry to lose the Vulcan to the disease and said he'd miss the "pointy-eared encyclopedia". (TAS: "The Pirates of Orion")
Captain Jean-Luc Picard displayed his amazement, when Data didn't understand the word "snoop", as Data was "programmed as a virtual encyclopedia of Human information", according to the captain. (TNG: "Encounter at Farpoint")