a journey, e.g. for business or pleasure, in which one returns to the starting point
a visit, e.g. to a historic site or factory, for pleasure or information
a guided tour of the castle
a series of professional engagements involving travel
a theatrical company on tour
(also tour of duty) a period during which an individual or unit is engaged on a specific duty, esp in one place
His regiment did a tour in Northern Ireland
[Middle English from Old French tourn, tour lathe, circuit, turn, from Latin tornus: see turn1]