(plural ca·su·ists) noun 1. somebody considering ethics and morals: somebody, especially a theologian, who tries to settle questions of ethics or morals by applying general rules and principles to them 2. somebody using misleadingly subtle reasoning: a subtle, sophisticated, and sometimes deceptive reasoner, especially on moral issues (disapproving) [Early 17th century. Via French < modern Latin casuista < Latin casus "event"]