What is apustaja in english?

Could you please clarify for me what exactly the term "apustaja" refers to in its original context? It's not immediately recognizable as a commonly used term in English, so I'm curious about its origin and meaning. Is it a technical term within a specific industry or field? Or perhaps it's a word from another language that has a direct translation in English? I'd appreciate it if you could provide some context or explanation to help me better understand what "apustaja" signifies.