head out:前往,启程,出发,到达,长出头状物,头向外例句：I have a long way to go before dark．I'm going to head out．天黑之前我还要走一大段路程，我得上路了。head off:拦截,改变话题,回避,赶在别人之前到达例句：The thief realized that the police were following him，but he succeeded in heading them off at the junction．小偷发现**在跟踪他，可是他在十字路口把他们甩掉了。