Falling headlong is a phrase that indicates a sudden, uncontrolled fall or plunge. It can also imply a recklessness or a lack of caution. Some synonyms for this phrase include tumbling, plunging, diving, hurtling, careening, hurtling, and hurtling headfirst. These words all convey a sense of suddenness and lack of control. Other synonyms might include plummeting, crashing, toppling, collapsing, or stumbling. Each of these words captures a different aspect of the idea of falling headlong, but they all suggest a sudden, uncontrolled motion that can be dangerous or even deadly.