敲定 is a resultative verb meaning 'to finalize' or 'to settle' after discussion or negotiation. It's more specific than 决定 (to decide) — it implies a process of bargaining or deliberation that ends with a firm conclusion. You'll hear it in business, contracts, and informal planning contexts. The verb can take an object directly (敲定方案) and can also be used with 得/不 for possibility (敲得定/敲不定).