on second thought
US /ɑːn ˈsek.ənd θɑːt/
UK /ɑːn ˈsek.ənd θɑːt/
1.
used to say that you have changed your mind or that you have a new idea that is better than your previous one
:
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I'll have the chicken, no, on second thought, I'll have the fish.
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Let's go to the park. Actually, on second thought, it might rain.