You can delete both default as well as manually created Circles from your Google+ profile which you no longer want to use.
Instructions:
- Login to your Google+ profile.
- Go to your Circles page.
- Right click on the Circle you want to delete and select delete Circle.

- After confirming to delete that Circle, the selected Circle will roll down to the Create New Circle.

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This is of LITTLE help. No good.
What I want is the ipad2 mobile phone version on how to delete cirlce!