Soutie means: An Englishman in South Africa or a white English speaking South African of British descent.. It is military jargon and mostly appears in service contexts, war fiction, or among veterans and their families. It carries sexual or vulgar connotations; not alarming on its own but worth understanding the context your teen heard it in. 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.