An Irish yell of victory or excitment.
After Brigadier General Thomas R. R. Cobb's Irish Regiment of Georgia pushed back Lieutenant Colonel St. Clair Mullholands Irish Brigade, a Captain (3 stripes on the collar) took off his hat and started yelling "Haroo! Haroo!" and the rest of the regiment cheered "Haroo!"
by Jedi_Master June 15, 2008