to stop someone or something: to hinder, prevent, or forbid
At its core this verb means to get in the way of something so that it does not happen. What is being stopped can be almost anything: people bringing children to Jesus, a stranger casting out demons, a traveler on the road, an official collecting a tax, even a prophet's reckless plan. In every case the action is the same, someone or something is held back.
English needs several words to cover its range. When a person is told not to do something, we usually say forbid. When an event or a journey is blocked, we say hinder or prevent. When a thing is held back from someone who asks for it, we say withhold. These are all the one Greek word doing its single job in different settings.
Because it names a plain, everyday action, the word carries no special weight on its own. Its force comes from what is being stopped. Peter's question at Cornelius's house, whether he could stand in God's way, and the Ethiopian official's question at the roadside, what was to keep him from being baptized, both turn on this verb, and in each the point is that no one should block what God is plainly doing.