What is ace slang for?

Excuse me, could you possibly clarify what you mean by "ace slang"? I'm not entirely sure what context you're referring to, as the term "ace" can have various meanings depending on the setting. In the realm of cryptocurrency and finance, for example, it's not a commonly recognized slang term. Could you perhaps elaborate on the specific context or culture you're referring to? It might help me provide a more accurate and relevant answer to your question.