Idiom Scenario 2:
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It is Monday morning. The boss has given you until Friday to create three new ideas that will speed up production in the factory where you work. You are going to be ...
under the gun
all week.
Idiom Scenario 3:
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It is Monday morning. You arrive at work to discover that the boss is handing out notices of job terminations. There had been talk that the company was going to reduce staff. You are lucky because you did not lose your job. You go and talk to your boss and ask her if your job is in danger. Your boss replies that ...
"Your job is under the gun. "
In this case,
under the gun means that there is a threat that your job may be terminated.