What does “write off as” mean in English?

In this sci-fi clip, a soldier explains: “At first, our field tech wrote it off as interference.” He means the team decided the strange readings weren’t important, and ignored them, before realizing they were wrong. To write something off as X means to dismiss it, deciding it’s just X, and not worth further attention. It often turns out that decision was a mistake.

You’ll hear it a lot in business and everyday talk: “Don’t write off his idea just because it sounds strange,” or “She wrote the noise off as the neighbors, but it was actually a leak.” “Write off” has a separate money meaning too (accepting a debt won’t be paid), but “write off as [something]” is always about dismissing or misjudging, not about cash.