herpes: a sexually transmitted infection caused by herpes simplex virus (HSV). Herpes can also be transmitted non-sexually (such as through kissing) and causes small, blister-like sores (cold sores) around the mouth or genitals. Herpes type 1 is typically associated with sores around the mouth, while herpes type 2 is typically associated with sores around the genitals or anus. Herpes cannot be cured, but the symptoms of genital herpes can be treated using antiviral medications.