1. I know about the surprise party you guys are throwing me today. Jerry let it slip earlier today.2. She let (it) slip that she's still in love with her ex husband.3. I am sorry your secret slipped out when I was talking to your wife.4. He blurted out the hiding place of the suspect.
 let (it) slip slip out blurt out這些用法都指不小心說出某些事情，也就是說溜嘴的意思
My sister is bad-temered and would snap at anybody whenever she feels like it.