a period of time spent in military service
"After his two-year tour, the soldier returned home to see his family for the first time since deployment."
A journey through a particular building, estate, country, etc.
"The old lighthouse was a tall stone tour that guided ships through the foggy harbor."
A tower.
In plain English: A tour is a planned trip where you visit many different places and then go back to where you started.
"The tour included visits to three local museums."
Usage: Use this noun to describe an organized visit where someone guides others around a specific place like a museum or city. It is distinct from simply traveling somewhere without the element of showing things to visitors.
To make a journey
"The driver toured the long line of cars ahead just to see if anyone was looking at him."
To toot a horn.
In plain English: To tour means to travel around different places for fun or work.
"We plan to tour the national parks this summer."
The Tour de France.
"After years of watching from home, I finally got tickets to watch a stage of the Tour de France in person."
The word tour comes from the Old French words tour and tourn, which were derived from the verb torner. It originally meant a turn or revolution before entering English with that same core sense of movement.