What domestic violence means
Domestic violence organizations define it as a pattern of behavior one partner uses to gain or keep power and control over the other. The National Domestic Violence Hotline lists physical, sexual, emotional and financial abuse as forms it can take. Physical violence matters a great deal. It just isn't the only way control works.
Emotional abuse, in the Hotline's words, includes non-physical behaviors meant to control, isolate or frighten someone. When it happens between partners, it's a form of domestic violence.