n.[C]

1. （船或飞机等的）舷窗
   I peeped out the porthole and saw a sea of clouds.

   我从飞机的舷窗向外张望，看到一片云海。

2. （堡垒或坦克等的）枪眼，炮眼，射击机
3. 【机】开口；汽门；水门

n.

1. a small window on the outside of a ship or aircraft.
2. historical an opening for firing a cannon through.