A stowaway is a person who hides on a boat, plane, or other vehicle without permission. Imagine you are going on a fun trip on a big ship or airplane. Before you leave, the grown-up people check the passengers to make sure everyone has a ticket and a seat. They do this to make sure they have enough food for the trip and to keep everyone safe. However, sometimes someone might not want to follow the rules or might not have money for a ticket, so they hide in a secret place like a closet or under a big box. This person is called a stowaway because they are not supposed to be there! Stowaways can be very dangerous because they are not checked to make sure they are safe to travel and they could cause trouble. It is always best to follow the rules and buy a ticket if you want to go on a trip.