Engaol means: To imprison in a gaol.. The word is mostly archaic or historical; you will only encounter it in old texts, period drama, or school history rather than current teen conversation. It comes from prison or criminal-justice contexts; worth knowing what media your teen is consuming. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.