A gackattack is when an individual who has consumed stimulants such as XTC, MDMA or speed is so affected by these drugs that they lose their shit. During a gack attack, one often does not have control of many muscle functions. Sweating tends to increase dramatically along with body temperature. A persons pupils are very large. A gackattack also directly influences ones brain and their thoughts are merely the beat of the music. Gackattacks are beautiful experiences if you love to doof, doof.