If something such as someone's reputation or career nosedives, it suddenly gets much worse. Since the US invasion the president's reputation has nosedived. Nosedive is also a noun. He told the tribunal his career had `taken a nosedive' since his dismissal last year
If prices, profits, or exchange rates nosedive, they suddenly fall by a large amount. The value of other shares nosedived by £2.6 billion. = plummet Nosedive is also a noun. The bank yesterday revealed a 30 per cent nosedive in profits