WordNet
n. a ceremonial escort for the (regimental) colors
Wikipedia
In military organizations, the Color Guard (or Colour Guard) refers to a detachment of soldiers assigned to the protection of regimental colors. This duty is so prestigious that the color is generally carried by a young officer ( Ensign), while experienced non-commissioned officers ( Colour sergeants) are assigned to the protection of the flag. These NCOs, accompanied sometimes by warrant officers (as is the case in several countries), can be ceremonially armed with either sabres or rifles to protect the color. Color guards are generally dismounted, but there are also mounted color guard formations as well.
Color guard can be found in most American colleges, universities, high schools, and independent drum corps. Color guard uses various equipment, such as flags, rifles, and sabres, along with dance, to express dynamic passages in the music accompanying the marching band show. Usually marching bands and color guards perform during football games at halftime, out of tradition. During marching band competitions, the guard adds to the overall score of the band and is also judged in a category usually called auxiliary.
Color guard has since evolved into a separate activity known as winter guard, which is an indoor sport where the guard performs unaccompanied by the band, to a piece of pre-recorded music, usually during the winter and spring. Winter guards compete independently in such circuits as Winter Guard International (WGI) and Tournament Indoor Association (TIA).