1. An exclamation of disgust or disapproval. Similar to ack!, gak! can mean a number of things, mostly in the negative connotation. Also, a sound that signifies the desire of the person to throw up.
  2. A children's toy. Launched in the summer of 1992 by Mattel, it is a nasty goo of various colors, of unknown composition and unlimited allure to little kids. Scientists suspect a water-based mixture of acrylic and silicone. Bouncy and stretchy, Mattel made a fortune off the stuff, putting it in the ranks of Silly Putty and Slime.
  3. An album by Aphex Twin. It contains four songs, Gak 1 to Gak 4, and is purely instrumental. They all have hard-driving beats and a very hypnotic rhythm. Panned by critics, it is nonetheless a good addition to the collection of any Aphex Twin fan. Gak 1 has an extremely interesting piano part, but my favorite is definitely Gak 4. Highly recommended music.