In*vol"un*ta*ry (?), a. [L. involuntarius. See In- not, and Voluntary.]

1. Not having will or the power of choice.

2. Not under the influence or control of the will; not voluntary; as, the involuntary movements of the body; involuntary muscle fibers.

3. Not proceeding from choice; done unwillingly; reluctant; compulsory; as, involuntary submission.

[[English]]
• without intention
       Ex. He involuntarily overheard the conversation. (He did not intend to, it just so happened.)
  
• against the explicit will
       Ex. He found himself the involuntary witness in the trial (He explicitly refused but was forced to testify.)