hold on

informal
used to tell someone to wait for a short time:
Hold on, I'll check in my diary.

informal
used to say that you are confused or surprised by something that you have just heard or read and want to understand it:
Now hold on, Ed, that wasn't what we agreed at all!

to manage to stay alive or to deal with a difficult situation:
We just had to hold on until help arrived.

to hold something or someone firmly with your hands or arms:
She held on tightly to his waist.
(Cambridge Advanced Learner's Dictionary & Thesaurus からの hold on の定義 © Cambridge University Press)

アメリカ英語辞典
to wait, esp. for someone to speak:
She’s on the other line – can you hold on?
(Cambridge Academic Content Dictionary からの hold on の定義 © Cambridge University Press)

ビジネス英語
to wait while someone else does something, especially when you are using the phone:
Can you hold on? I'll try to connect you.
Hold on, I'll be with you in a minute.

to continue to do something difficult while waiting for help:
Can you hold on for just a few more minutes? Then you can take a break.
(Cambridge ビジネス英語辞典 からの hold on の定義 © Cambridge University Press)

- Cambridge Dictionary