"A grouping of signs and symptoms, based on their frequent co-occurrence, that may suggest a common underlying pathogenesis, course, familiar pattern, or treatment selection.
Subsyndromal: below a specified level or threshold required to qualify for a particular condition. Subsyndromal conditions (formes frustes) are medical conditions that do not meet full criteria for a diagnosis—for example, because the symptoms are fewer or less severe than a defined syndrome—but that nevertheless can be identified and related to the "'full-blown" syndrome."
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. Fifth Edition. Washington, DC. American Psychiatric Association. 2013. Page 830.