1. to associate or interact in a friendly way with someone, especially someone from a different group or background
Usage: British spelling (American: fraternizes); third person singular present tense
2. to have friendly relations with an enemy or opposing group, especially in a military context
Usage: often used in historical or military contexts; third person singular present tense

Examples

• She fraternises with people from all walks of life at the community center.
• The soldiers were warned not to fraternise with the local population.
• He fraternises regularly with his colleagues outside of work.
• The two rival teams fraternise before the match begins.
• After the conflict ended, the former enemies began to fraternise cautiously.
• She fraternises with international students to improve her language skills.