How would you define a bug?

First we will write bug description about bug type. And will define the environment ( Browser or environment thing) with bug ID, Along with Test steps then we have to write expected results and actual results along with screen shots (LOGS).

If the test does not meet the requirement then that is bug.

if there is a mismatching between expected and actual result it is called bug......to define a bug we have to provide the following details like summary of the defect, priority, severity, assigned to whom(Developer name), detected by(tester name), which version the bug has been identified, which module the bug has been identified, whether the bug is a reproducible one or not, description where you write steps to reproduce the bug along with the screen shot as an attachment