As per my information Defect and Bug are the same .
I have read some of the article of eminent personalities like James Bach,Cem Kaner,Rex BLack etc and they have used those term one instead another.I think if it has been asked in any interview then it is just to see how you react if different words of same meaning is thrown to you.
Similar example of like this in real world scenario
1. Electricity and Power
2. Mobile and Cell
Defect and Bug are same meaning words adopted by different organization.
Well, There are many definitions but it is matter of perspective
Defect is something that is perceived by end user as 'not working' or 'not useful' pr 'not upto his expectations'. He may say it is a defect. When this defect goes to developer, then he may classify it as a Bug or a feature or a 'not requested' feature or problem with user usage.
Eg. Some mail clients automatically add the mail sender to user's contact list. User can say it is a defect as he has not added it but the mail client developer can say it is not a bug but a feature
actually we have many terms that leads to software failure:
1- A Human can make an Error (aka a Mistake)
- An Error is ‘A Human Action that produces an Incorrect Result’
2- The Error can cause a Defect (aka a Fault or Bug)
- A Defect is ‘A flaw in a component or system that can cause the component or system to fail to perform its required function’
- A Defect can be in the Software, System or in a Document
# failure: ‘Deviation of the component or system from its expected delivery, service or result’