Another way to find out what a shovel is, is to lift your opponent up in the first few turns and start pushing him outside the dojo. If they start raging and flaming you shouting things in caps like "YOU F*%K#@G NOOB SHOVELER" then it is considered a shovel. Alternatively they might just quit before they lose.

Some people have also tried to give advice on how to counter it. The best way, this you wont see done a lot, is simply to lean back if you see them using a shovel like opener. By leaning back, when your opponent tries to push you, they will push themselves off the ground and you will lift them. In Some cases this can even reverse a shovel.