They were taking pot-shots at empty cans on trees in the forest.

pot-shots 是由 pot（罐子）和 shot（射击）组成的复合词，字面意思是"射击罐子"。 shot 是名词，指"射击、开枪"的动作。 pot-shots 引申为"随意射击、漫无目的的射击"，常用来形容不瞄准就随意开枪的行为。