He's been pining away since his wife died and is a shadow of his former self.
The lecturer asked the students to pipe down and pay attention.
At first, no one answered, then finally someone piped up.
pit * against
The war pitted neighbor against neighbor.
pitch for +
He pitched for the job, but they gave it to someone else.
We were behind schedule, but the others pitched in and we got it done in time.
pitch into +
嚴厲批評 (某人)；攻擊 (某人)
The shareholders pitched into the management about their pay rises at the meeting.
(為了使某人高興或得到自己想要的東西而) 假裝同意或接受 (某人，某觀點等)
I disagreed with the idea but I had to play along because everyone else liked it.
The children were play around and being annoying.
play at +
把...不當一回事；對 (某事) 敷衍了事
He just plays at being a lawyer- he never wins a case.