Truculentus is a big word that describes someone who is very mean and aggressive. Imagine if you were playing with a toy and someone came up and took it away from you, yelling and pushing you. That person might be called truculentus because they are being really mean and not being nice to you.
Basically, truculentus is a word that describes someone who bullies or uses force to get what they want. It's important to remember that nobody should be treated that way and we should always try to be kind to others.