(aviation) The rapid, uncontrollable descent of an aircraft in a steep spiral. / (figuratively) A severe mental or emotional collapse; emotional breakdown.

Of an aircraft: to go into a rapid, uncontrollable descent in a steep spiral. / (figuratively) To go into a sharp, sustained, often uncontrollable descent or decline.

plural of tailspin

simple past tense and past participle of tailspin

present participle of tailspin