"Unavoidable collision" refers to a situation where two objects or individuals are going to collide or crash into each other, and there is no way to prevent or avoid it from happening. Full definition
Helps brake the vehicle when it senses an otherwise unavoidable collision with a vehicle detected in front of you. (automobiles.honda.com)
CMBS (Crash Mitigation Braking System): helps brake the vehicle when it senses an otherwise unavoidable collision with a vehicle detected in front of you (driveclassichonda.com)
The Pre-Collision control will stiffen the suspension of the vehicle, retract the front seat belts, and initializes the BrakeAssist system to prevent injury during an unavoidable collision. (automotive.com)