Wiktionary
tour guide
n. A person who provides assistance and information to people on organised tours.
WordNet
tour guide
n. a guide who leads others on a tour
Wikipedia
Tour guide
A tour guide (U.S.) or a tourist guide (European) provides assistance, information and cultural, historical and contemporary heritage interpretation to people on organized tours and individual clients at educational establishments, religious and historical sites, museums, and at venues of other significant interest.