The simultaneous execution of more than one task. For example, a computer that launches or runs more than one program simultaneously is multitasking.
This term has expanded to include human activities, such as talking on the phone, IM'ing, doing homework, listening to music, and eating lunch at the same time. A sign of our times is how adults observe young people and are amazed at their ability to multitask.
A modern version of this definition is the attempt by human beings to operate like computers, often done with the assistance of computers. Many people think that multitasking enables you to be more productive and more efficient, however, studies have shown that multitasking actually slows our thinking because it forces us to chop competing tasks into pieces, review the rules for putting the pieces back together, and then attempt to do so in a different manner. In other words, a brain attempting to perform two tasks simultaneously will, because of all the back-and-forth stress, exhibit a substantial lag in information processing.