Which word means to fall or be thrown headfirst, often indicating a rapid or heedless action?

The word that best captures the meaning of falling or being thrown headfirst, often signifying a rapid or heedless action, is "plunge." This term conveys a sense of suddenness and force, typically associated with diving or dropping quickly into a lower position or state.

While "precipitate" can imply a hasty action or a sudden occurrence, its usage often aligns more with causing something to happen abruptly rather than the physical act of falling. "Collapse" suggests a failure or breakdown in structure rather than the act of falling into something headfirst, and "descend" simply refers to moving down, lacking the connotation of speed or recklessness. Thus, "plunge" stands out as the most fitting choice for the described action.