To faint is "close to losing consciousness" or "briefly lose consciousness" according to the Concise Oxford.

Fainting is one of the many situations where you lose consciousness. You can also lose it when you are asleep or when you are in Coma. They also say that saints who meditate lose consciousness.

To understand more, you need to see what consciousness means:

Oxford says it is the state of being able to use your senses and mental powers to understand what is happening:

Cambridge says it is being awake, thinking and aware of what is happening around you:

Webster says: It is the state of being characterized by sensation, emotion, volition, and thought.

As you can see, fainting is only one situation where you lose consciousness.

Hope this helps:-))