push comes to shove

ＳＦのThe Martian by Andy Weirを読んでいます。
"If I can't reach Mark, I want you to release my tether."
"Dr. Beck," Vogel said, "the commander has said no to this."
"I know what the commander said, but if I need a few more meters, I want you to cut me loose. I have an MMU, I can get back without a tether."
"I will not do this, Dr. Beck."
"It's my own life at risk, and I say it's okay."
"You are not the commander."
Beck scowled at Vogel, but with their reflective visitors down, the effect was lost.
"Fine," Beck said. "But I bet you'll change your mind if push comes to shove."
Vogel did not respond.
"push comes to shove" は3/28/2009に取り上げていますが、その時は辞書で確認しなかったので、今日は辞書の説明を見ます。
辞書には "when push comes to shove" の項で説明があります。
・Oxford English Dictionary: When one must commit oneself to an action or decision.: ‘when push came to shove, I always stood up for him’
・Wiktionary: When the pressure is on; when the situation is critical or urgent; when the time has come for action, even if it is difficult. He is not a particularly talented builder, but when push comes to shove, he can usually get the job done.