What's it mean and when's it used?

Native speaker’s answer
Rebecca
"Not this time" means that something or an outcome happened before, but the person won't let or allow it to happen again. It's a statement said when someone is determined or adamant about something being different than before. Ex: You may have won last time, but not this time. Ex: This time, everything will be different on our trip. Ex: Not this time, Shaun. Go home.