frat ‧ er ‧ nize BrE AmE ( also fraternise British English ) /ˈfrætənaɪz $ -ər-/ verb [intransitive]
to be friendly with someone, especially if you have been ordered not to be friendly with them
fraternize with
The troops were forbidden to fraternize with the enemy.
—fraternization /ˌfrætənaɪˈzeɪʃ ə n $ -tərnə-/ noun [uncountable]