noun - a situation in which somebody has been challenged to do something or asked to prove that they are brave enough to do something

verb - to make someone familiar with a new place, situation, or system, or to find your position or direction in relation to your surroundings

verb - to allow someone to experience the consequences of their actions or mistakes, often by leaving them to worry or suffer without offering help

verb - to place a mark next to an item on a list to indicate that it has been done, bought, finished, dealt with etc.

verb - to keep something or somebody in a dangerous situation from which they want to escape but cannot, or to prevent them from escaping

verb - to leave a company or an organization because you think it is about to fail or you want to join a rival organization

noun - a system that enables people to talk to each other across large distances, you need a number to call somebody using this system

noun - a device that connects the computer to telephone lines in order to send and receive e-mails and connect to the internet etc.