The act of penetrating a potato, celery or a carrot into the a-hole vigorously. Depending on preference before the penetration you or the person you are sexually pleasuring might like to take a big SHAT on the desired vegetable.
"Last night I got a juicy veggie moin, and Shaun SHAT on the carrot before sliding it into my tight anus"
Instead of breakfast cereal and milk, you put raw vegetables in a bowl of ice water and it is eaten by hand or with a knife (stabbing the vegetable and eating it).
Guy 1: Hey how's you diet going?
Guy 2: Very good! I've been eating VeggieCereal instead of breakfast cereal.