Real Dictionary

guide
In Britain, Guides is an organization for girls which teaches them to become practical and independent. Guides used to be called the Girl Guides. In the United States, there is a similar organization called the Girl Scouts.
countable noun: A guide is a book that gives tourists information about a town, area, or country.
countable noun: A guide is a book that gives you information or instructions to help you do or understand something.
countable noun: In Britain, a Guide is a girl who is a member of Guides.

guide in American English
a person or thing that guides
to act as a guide
to point out the way for; direct on a course; conduct; lead
noun: a person who guides, esp. one hired to guide travelers, tourists, hunters, etc
transitive verb: to assist (a person) to travel through, or reach a destination in, an unfamiliar area, as by accompanying or giving directions to the person

guide in British English
noun: a member of an organization for girls equivalent to the Scouts
noun: a person, animal, or thing that guides
verb: to lead the way for (a person)

guide in Mechanical Engineering
noun: A guide is a device that directs the motion of a tool or machine part.