n.[C]

1. （船或飛機等的）舷窗
   I peeped out the porthole and saw a sea of clouds.

   我從飛機的舷窗向外張望，看到一片雲海。

2. （堡壘或坦克等的）槍眼，砲眼，射擊機
3. 【機】開口；汽門；水門

n.

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