The term commonly refers to an opera that employs epic themes and exhibits them through the use of a large orchestra and chorus. An example of grand opera is Verdi's Aida, with its large processional scene in which hundreds of singers, dancers, and animals share the stage.
The term normally given to the genre that flourished in Paris from the early 1820s and which remained influential beyond the frontiers of France throughout the 19th century and even into the 20th century. Grand Opera is entirely sung from start to finish, as opposed to opera that may have spoken dialogue. It is often epic in scale and, in the case of 19th century French opera, may have a full-scale ballet inserted in the middle of the work. Grand Opera frequently deals with serious, dramatic subjects. La bohème, Tosca, Turandot, and Aida are all considered grand opera.