verb

cause (someone) to lose confidence or hope.

the General Strike had demoralized the trade unions

dishearten,dispirit,deject,cast down,depress,dismay,daunt,discourage,unman,unnerve,crush,sap,shake,throw,cow,subdue,undermine,devitalize,weaken,enfeeble,enervate,break someone’s spirit,bring someone low,knock the stuffing out of,knock for six,knock sideways,dispirited,disheartened,downhearted,dejected,downcast,low,depressed,despairing,disconsolate,crestfallen,disappointed,dismayed,daunted,discouraged,unmanned,unnerved,crushed,humbled,cowed,subdued,sapped,drained,shaken,thrown,undermined,devitalized,fed up,brassed off,cheesed off,pissed off