Crop-dust: 1. The act of trailing a stream of gaseous material as one walks by an unsuspecting bystander. 2. When one passes gas around another and then escapes as if nothing ever happened. 3. The use of "Shake", or leftover weed dust, to sprinkle over a full bowl pack. 4. The act of spraying crops with fertilizers, pesticides, or fungicides from an agricultural aircraft. The overall ventilation was not too good and it definitely didn't help that someone crop-dusted as they got off on the 4th floor.