This expression is used to indicate that there is no other choice or possibility besides the one described in the preceding clause. It corresponds to "have no choice but to" or "can't help but" in English.
Details
Examples
<span class="speaker-a">가:</span> 여보, 옷을 또 사려고?<br><br><span class="speaker-b">나:</span> 유행에 뒤떨어지지 않으려면 옷을 자주 <span class='focus'>살 수밖에 없어요.</span>
A: Dear, are you planning to buy any more clothes? B: If I am to keep up with fashion trends, then I have no choice but to buy clothes often.
<span class="speaker-a">가:</span> 환경오염 문제가 점점 더 심각해지고 있어서 큰일이에요.<br><br><span class="speaker-b">나:</span> 맞아요. 환경을 보호하지 않으면 앞으로 인류는 멸망<span class='focus'>할 수밖에 없을 거예요.</span>
A: Environmental pollution is getting worse, and it's a big problem. B: Right, If we don’t protect the environment, mankind will be unable to avoid extinction.
<span class="speaker-a">가:</span> 현금으로 내려고요?<br><br><span class="speaker-b">나:</span> 이 가게에서는 신용카드가 안 된다고 하니까 현금으로 <span class='focus'>낼 수밖에 없네요.</span>
A: Are you planning to pay with cash? B: This store apparently doesn’t take credit cards, so I have no choice but to pay with cash.