A Grito (Spanish pronunciation: ['??ito], Spanish: Shout) is a common Mexican interjection, used as an expression of joy or excitement, that has become one of the internationally known behaviors of typical Mexican culture.
Video Grito
Characteristics
This interjection is similar to the yahoo or yeehaw of the American cowboy during a hoedown, with added Ululation trills and onomatopoeia closer to "aaah" or "aaaayyyyeeee", that resemble a laugh while performing it.
The first sound is typically held as long as possible, leaving enough breath for a trailing set of trills.
Maps Grito
Usage
The Grito is sometimes used as part of the official remembrance of the Shout of Dolores, during the celebration of the Mexican Independence Day.
Although the Grito Mexicano has patriotic connotations, it is more commonly used in non-formal settings, where it is belted at crowded celebrations or parties with friends and family. The normal position for the yell to be inserted is after a toast, or during a very familiar song (at a musical interlude, a bridge or after the first few notes) either by the performer or excited members of the audience.
It's commonly done immediately prior to the popular Mexican war cry: "¡Viva Mexico, Señores!" (Long live Mexico!, Gentlemen!), or its more rough version "¡Viva Mexico, Cabrones!" (Spanish for: Long live Mexico, Cabrones!).
In rural areas it is also common to see people do celebratory gunfire, before or after the shout.
References
Source of the article : Wikipedia