Altseason refers to a period when altcoins see rapid price increases as capital shifts from Bitcoin, often lasting weeks to months. Key indicators include rising altcoin dominance, declining Bitcoin dominance, and strong market trends. The 7-year trendline in the chart suggests a potential breakout, but timing depends on Bitcoin's price action, investor sentiment, and macroeconomic factors. No fixed timeline exists for altseason in 2025, but historical cycles show peaks every 4 years in bull markets.