not similar; "a group of very dissimilar people"; "a pump not dissimilar to those once found on every farm"; "their understanding of the world is not so dissimilar from our own"; "took different (or dissimilar) approaches to the problem"
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"