Full-stack
A developer who can build both the screens people use and the server code behind them, in the same application.
What it tells you about a developer
A genuinely full-stack senior owns complete features and makes tradeoffs across the whole system, which is worth a great deal to a small team. Two questions settle it: which side they would pick for the hardest work, and whether one project shows their commits on both sides. The word covers a wide range of experience, so read it alongside the seniority evidence.
Full-stack means one person carries a feature from the database to the screen with no handoff. Nearly all full-stack developers have a stronger side, and job descriptions apply the label loosely.