When a fully clothed woman walks by you and her breasts quickly rub against your body because she needs to squeeze through a tight space or because she wants to give you a quick example of the firmness of her breasts. The breasts swipe you like a credit card being swiped.
"When Peggy was moving from the bar to the dance floor she cropdusted me." or "When Annya was climbing out of the fire engine, she cropdusted me." or "Tasha likes to cropdust everyone." or "Amanda likes to cropdust me in private."