the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate)
not subject to the control of the will; "involuntary manslaughter"; "involuntary servitude"; "an involuntary shudder"; "It (becoming a hero) was involuntary. They sank my boat"- John F.Kennedy
controlled by the autonomic nervous system; without conscious control; "involuntary muscles"; "gave an involuntary start"
the complex of all the attributes--behavioral, temperamental, emotional and mental--that characterize a unique individual; "their different reactions reflected their very different personalities"; "it is his nature to help others"
a person of considerable prominence; "she is a Hollywood personality"