Loss of the will or fighting spirit; often used in military contexts but also figuratively for losing motivation in work, sports, etc.
長期の戦闘で多くの兵士が戦意喪失に陥った。
After prolonged fighting, many soldiers fell into a loss of fighting spirit.
連敗続きでチームの戦意喪失が心配されている。
With a string of losses, there are concerns that the team is losing its fighting spirit.
会社の方針変更に失望し、彼は仕事で戦意喪失している。
Disappointed by the company's policy change, he has lost his fighting spirit at work.