Fraternize vs. Fraternise

To associate with others in a friendly and informal way.

Standard spelling of fraternize

To associate on friendly terms with an enemy or opposing group, often in violation of discipline or orders.

Be on friendly terms with someone, as if with a brother, especially with an enemy

To associate on friendly terms with one's superiors or subordinates, often in violation of policy.

(intransitive) To associate with others in a brotherly or friendly manner.

(intransitive) To associate as friends with an enemy, in violation of duty.

(intransitive) To socialize in confidentiality.

(intransitive) To have an intimate or sexual relationship with a forbidden party.

To associate or hold fellowship as brothers, or as men of like occupation or character; to have brotherly feelings.

To bring into fellowship or brotherly sympathy.

Be on friendly terms with someone, as if with a brother, especially with an enemy