So, who is a Tester?

The other day I and Sunil were having a discussion around the above topic. It started off by me asking him a question, " Who is a real tester?"....Sunil thought off for some minutes and then came a reply, "A tester is a person who is a member of the test team in the project and is responsible for ensuring that the product/application works as expected under controlled conditions."
Well yes, most of us would agree to the above definition of a tester...but I gave a thought around this and felt that the real tester is actually the end user of the application. He is the one who tests the product/application under real environment and not the test environment unlike the so called testers in the project team. He may not have the technical skills that the testers possesesWe as testers just try to simulate the environment in which the application would be eventually used but we fail to identify the gaps! This is where the bugs get leaked.
We try to focus on just the requirements and not realizing the way the end users would be using the application.
As a first step, get to hear from business what are their expectations from the application. How they would want to use it.