Disassociate is another spelling of dissociate. It means to cut the link between you and something — a person, a group, an idea, or even a feeling. A company might disassociate itself from a rude advertisement. A public person might disassociate from an old remark. Doctors also use dissociate when a mind seems to step away from a painful memory; that use is more often spelled dissociate. In ordinary English the two spellings mean the same thing. Dissociate is a little more common in careful writing, but you will meet both. It is not a casual word. People reach for it when they want a clean, public break, not a soft “I don’t really agree.”