UK definition (RCEM): It describes the sudden onset of aggressive and violent behaviour and autonomic dysfunction, typically in the setting of acute on chronic drug abuse or serious mental illness.

Australian definition (NSW Health): Behaviour that puts the patient or others at immediate risk of serious harm and may include threatening or aggressive behaviour, extreme distress, and serious self-harm which could cause major injury or death.

There are some superb resources on the Life in the Fast Lane site on this topic. Really recommend having a look!

There is a useful summary on some de-escalation strategies & techniques, from HSI here.

This handbook from a UK NHS Trust outlines some key principles from their conflict resolution training.

JRCALC Clinical Guideline: Acute Behavioural Disturbance. 

NICE. NG10. 2015. Violence and aggression: short term management in mental health, health and community settings.

RCEM. Best Practice Guideline. 2016. Guidelines for the Management of Excited Delirium/Acute Behavioural Disturbance.

Faculty of Forensic and Legal Medicine. 2019. Acute behavioural disturbance (ABD): guidelines on management in police custody.

College of Paramedics. Acute Behavioural Disturbance Position Statement

The CQC brief guide to restraint