Someone who was assigned the incorrect gender at birth. This person feels very ashamed of their body and the genitals that they were given at birth so decide to have multiple surgeries and start cross-sex hormones to make them appear as their correct gender.

The feeling that most transgender people feel about their body is called 'Gender Dysphoria'. The 'gender dysphoria' feels different to everyone. It can feel like you just need to change what you look like mildly but it usually feels like there is no way that you can live in the body that you were assigned at birth.

Identifying as a different gender from the one you were assigned at birth.

Transformers or something I don’t know

Transgender (adj.) – According to Google
Denoting or relating to a person whose self-identity does not conform unambiguously to conventional notions of male or female gender.

Plainer English
Referring to a person whose thought of themselves doesn’t line up with one accepted idea of being a man or woman.

As simple as I can get it
a person who thinks of themselves as a man or woman even though they have the opposite sex organs.

In terms of the English language the word Trans means to change or switch. Biologically it is impossible for one to change their gender as they cannot change their DNA to that of the opposite gender only their hormones and body parts which scientifically have never defined ones gender as there has always been men with a lack of testosterone or born without a penis for example. Taking this we can then come to the conclusion that seeing that one cannot not biologically change their gender they cannot be trans gender as a change or switch has not been made to their gender they cannot be transgender.
A closing statement then: Transgender's scientifically cannot exist

One who is confused