combat
com·bat
I
 /ˈkɑːmˌbæt/  noun   [  noncount  ]
  : active fighting especially in a war
   troops ready for combat
   Some of these soldiers have never seen combat.
   He was killed in combat.
   armed/unarmed combat
  — often used before another noun
   combat operations/missions
   combat boots
   a combat zone
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com·bat
II
 /kəmˈbæt/  verb  , -bats, -bat·ed  also   -bat·ted, -bat·ing  also   -bat·ting [  + obj  ]
  1 : to try to stop (something) from happening or getting worse
   The drug helps combat infection.
   She dedicated her life to combating poverty.
   Exercise can help combat the effects of stress.
   The mayor pledged to combat crime.
  2 formal : to fight against (someone) : to engage in combat against (an enemy)
   They have been combating the rebels for months.