free fall 或 free-fall

free-fall的音标和读音：
DJ音标发音： [ˈfri:ˌfɔ:l]
KK音标发音： [ˈfriˌfɔl]

free-fall的词性：
n.（名词）

1. The fall of a body within the atmosphere without a drag-producing device such as a parachute.
自由下落：大气层里的、没有阻碍性装置（如降落伞）的物体的下落

2. The ideal falling motion of a body that is subject only to the earth's gravitational field.
自由下降：只有在地球的重力场中才能实现的物体理想的下降运动

3. Rapid, uncontrolled decline:
迅速的、不受控制的下降：

“The markets threatened to go into free fall and we came within an eyelash of . . . an uncontrollable panic”(Felix Rohatyn)
“行情有迅速下跌的危险，我们已到了…无法控制的边缘”(费利克斯·罗哈廷)