Behcet's syndrome: A chronic disease featuring inflammation of small blood vessels and characterized by a triad of features: ulcers in the mouth, ulcers of the genitalia, and inflammation of the eye (uveitis). The mouth ulcers typically present as recurring crops of aphthous ulcers. Arthritis is also commonplace. The cause of Behcet's syndrome is not known. It is more frequent and severe in patients from the Eastern Mediterranean and Asia than in those of European descent.