在各類競(jìng)爭(zhēng)場(chǎng)合，為了獲得私利，總有人會(huì)出賣隊(duì)友、犧牲朋友。這種行為就像大家同坐在一輛車上趕往目的地，他們卻選擇中途把自己的同伴推下車。

To underbus means to unfairly discredit, blame, or dispose of an ally or colleague, particularly for personal gain.
Underbus指為了個(gè)人私利，不公平地詆毀、責(zé)難或者拋棄同伴或者同事的行為。

This verb is a tidy shortening of the longer idiomatic phrase “to throw (someone) under the bus,” which has been in the language since at least 1991:
這個(gè)詞是短語“to throw (someone) under the bus”的簡(jiǎn)寫形式，意為：將某人推下水，即為了個(gè)人利益犧牲或者背叛別人。這個(gè)短語至少在1991年時(shí)就開始使用了：

Dees said he talked to Hood after he bonded out of the El Paso County Criminal Justice Center on Sept. 26, 1990, and warned him “that he was being thrown under the bus by Jennifer Reali.” But he said Hood believed Reali “was going to tell the truth.”
迪斯說，1990年9月26日胡德從埃爾帕索縣刑事司法中心保釋出來后，他曾經(jīng)警告過胡德“詹妮弗會(huì)讓他背黑鍋”。可是，胡德說他詳細(xì)詹妮弗會(huì)“實(shí)話實(shí)說”。

—Erin Emery, “Hood talks without thinking, friends testify at murder trial,” Gazette Telegraph, December 12, 1991

For example:

You can’t underbus key staffers during a campaign. Can you? May as well underbus yourself.
你不能在活動(dòng)期間背叛骨干員工，對(duì)不對(duì)？沒準(zhǔn)最后會(huì)把你自己也拖下水呢。

（中國日?qǐng)?bào)網(wǎng)英語點(diǎn)津 Helen）