What is the Definition of Definition?

What is the definition of definition?

I was in my Artificial Intelligence class and the lecturer, who had a habit of making conversations between the lecture, asked us a question. “I come to the university alone, in a car that can carry four people at least. Am I using more resources than I should? Am I doing something wrong?”

All of us in class had different opinions to that question.

“I’m thinking of buying a rickshaw” He added. “My family refuses to let me ride a bike because it’s dangerous. A rickshaw would be cheap, and I won’t be wasting the resources I have.”

All of the kids in the class started laughing. It was ridiculous. A high-profile lecturer at a well-reputed university, commuting in a rickshaw. That would be a sight. I also, didn’t agree to the argument of wasting resources either because I believe people have a right to spend on comfort.
Anyway,
We all asked the same question, “What will people say when they see you?”

“What is the definition of definition?” He replied.
“We define something by its functionality. The definition of clothes would be a cover for your body. It wouldn’t be a good looking, expensive fabric that will make you look like the life of a party .” He added.

“If something isn’t included in the definition, why do we think about it so much?” He asked.

We were all blank as if he has asked us a complex math question.

“We care so much about it because, we have our own definition of everything. We need to change that.”

I didn’t expect him to make sense, initially. But he did. He very well made sense.