involuntary

形容词 involuntary:

1. not subject to the control of the will- John F.Kennedy
   同义词：nonvoluntary, unvoluntary
2. controlled by the autonomic nervous system; without conscious control

1. An involuntary of joy escaped from her lips.
   她那情不自禁的喜悦脱口而出。
2. A sudden, involuntary, spasmodic muscular contraction causing severe pain, often occurring in the leg or shoulder as the result of strain or chill.
   痉挛一种由于紧张或寒冷而导致的肌肉突发性、无意识的、间歇性的紧缩，能导致剧烈的疼痛，通常发生在腿部或肩部
3. The involuntary and consistent response of an organism to a given stimulus.
   生理反应生物体对所受到的刺激作出的无意识的连贯反应
4. She gave an involuntary smile.
   她不由自主地笑了笑。

in.vol.un.tar.y

adj.（形容词）
Acting or done without or against one`s will:
非自愿的：无意或非本意而做的：
例句：
an involuntary participant in what turned out to be an argument.
无意中参加了一场争论的人

Not subject to control of the volition:
不自觉的：不受意志力控制的：
例句：
gave an involuntary start.See Synonyms at spontaneous
不禁吓了一跳参见 spontaneous

【引伸】
invol.untar.ily
invol.untar.iness
n.（名词）