widespread devastation, destruction
"The hurricane left a trail of havoc across the coastal town, leaving roofs torn off and streets blocked by debris."
To pillage.
"The invading army swept through the village, leaving nothing but ruins as they committed acts of havoc on every home they found."
A cry in war as the signal for indiscriminate slaughter.
"When the bugler blew the harsh note of havoc, the soldiers immediately charged forward to cut down anyone they saw without distinction."