A gurtgurt is someone who gives very sloppy oral sex. However, it can also be used as an insult with negative connotation or with positive connotation affectionately; it depends on who said it to you and how.
Negative: "You're such a dumb fucking gurtgurt- delete your account."
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.