Involuntary means happening without your conscious choice or control. When you blink, yawn, or hiccup, these are involuntary actions: your body does them automatically whether you want it to or not. Your heart beats involuntarily, pumping blood without you having to think about it.

The opposite is voluntary, meaning done by choice. Raising your hand in class is voluntary. Sneezing when pepper tickles your nose is involuntary. You can sometimes suppress an involuntary action briefly, like holding back a sneeze, but eventually your body overrides your will.

The word also describes situations where someone is forced to participate against their wishes. A passenger on a plane delayed by weather becomes an involuntary participant in a long wait at the airport. During America's military draft in past wars, some soldiers were involuntary members of the armed forces, meaning they were required by law to serve rather than choosing to enlist.

Understanding this word helps clarify who has control in a situation. When something is involuntary, responsibility or blame often shifts: you can't fault someone for an involuntary flinch or gasp any more than you can praise them for their involuntary breathing.