Nigger moment means: A moment in which emotion or ignorance overpowers one's rationality, causing an outburst of irrational aggression.. It is informal slang, fine in casual speech but not suited to formal contexts. It is generally derogatory or offensive; worth a quiet word about how it lands on the person being described. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.