a piece of artillery; a cannon; a gun

• 一门大炮

a piece of artillery; a cannon; a gun的用法和样例：

例句

1. The army trained its cannon on the fort.
   这支军队把一门大炮对准了那座碉堡。
2. The median line in the trajectory of fire of an artillery piece.
   中线一门大炮开火的轨迹中线。