( BrE also frat·er·nise ) / ˈfrætənaɪz; NAmE -tərn-/ verb
[ v ] fraternize (with sb) to behave in a friendly manner, especially towards sb that you are not supposed to be friendly with :
She was accused of fraternizing with the enemy.
► frat·er·niza·tion , frat·er·nisa·tion / ˌfrætənaɪˈzeɪʃn; NAmE -tərnəˈz-/ noun [ U ]
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WORD ORIGIN
early 17th cent.: from French fraterniser , from medieval Latin fraternizare , from Latin fraternus brotherly, from frater brother.