a walking dictionary, encyclopedia, etc.
a walking dictionary
A person who has a very large vocabulary or knows the definition of many words and who can recite them when asked. You should ask my brother what it means—he's a walking dictionary! Compared to most sixteen-year-olds, Sarah is a walking dictionary. She must read a lot in her spare time.
a walking encyclopedia
A person who has a very large and detailed knowledge of a diverse array of facts and who can recite them when asked. Lily's like a walking encyclopedia when it comes to reptiles.
a walking ˈdictionary, encycloˈpedia, etc.(informal) used to describe a human or living example of the thing mentioned: Geoff is a walking encyclopedia. He knows about everything. ♢ She’s a walking dictionary (= she knows a lot of words).
See also: walking