noun · people acting as informants or scouts to gather intelligence for someone else

他在敌方阵营中安插了许多耳目。

noun, adjective · referring to the senses of hearing and sight; sensory perception.

爷爷虽然年纪大了，但依然耳目聪明，听得见远处的声音。

noun · one's eyes and ears or the information and knowledge gained through them

旅游能增长见识，充实耳目。

expression · the attention, observation, or scrutiny of others

他做的那些坏事是无法掩人耳目的。