Meaning: used to refer a friend who is not reliable in difficult times.
someone who is a friend only when things are going right and leaves you when you face a trouble

Example Sentences:
1. Simran is looking for a loyal friend, not a fair-weather friend.
2. I really had thought that she would help me with my problem, but she is a fair-weather friend.

ラウンジ英会話では、役に立つ英語フレーズをたくさん身につける事が出来ますよ♫

Meaning: work together in order to achieve something that both groups want.

Example: 
Environment protesters have made common cause with local people to stop the setting up of the factories and iron industries on fertile land.

ラウンジ英会話では、役に立つ英語フレーズをたくさん身につける事が出来ますよ♫

Meaning: to succeed to survive in bad financial situations. To keep itself out of trouble in any difficult situation.

Example Sentences:
1.- I have to work 60 hours a week just to keep my head above water. I don’t know how people do it.
2.- With my new promotion at work it has been a struggle to keep my head above water.

ラウンジ英会話では、役に立つ英語フレーズをたくさん身につける事が出来ますよ♫