A close up of a yellowjacket.
The definition of a yellowjacket is a small insect in the wasp family; but, is not a wasp. It has black and yellow or black and white markings. The common name for this insect is often spelled "yellow jacket." However, according to the Entomological Society of America (ESA) the correct common name of this insect is "yellowjacket."
An example of a yellowjacket is a German yellowjacket with yellow and black markings that is found in the United States and is known to sting many times if provoked.