Austin was a cyborg; part organic and mechanical. A robot is all mechanical, 100% metal/plastic/artificial with no organic in them. Any organic, makes it a cyborg, they are consider enhancements.
The robots in Robot Combat League were pretty big, but I don't recall anyone calling them giants. I'd say anything significantly larger would qualify.Now define "giant".
Is Robocop a robot? Human face and hand, yet has "robo" in his name.
How about a mech/jaeger? Full human pilot.
Must a robot be autonomous, or can it have a crew? Internal crew, or remote crew? A bomb-disposal "robot", or flying drone, or a tank?
Being nitpicky - in the world of chemistry, lubricating oils and plastics are "organic". Anything with carbon in it is organic from a chemist's point of view. Might want to note that it is *living* parts that make it a cyborg, to be clear.
If someone created a machine that had cultured tissue muscles, but no living brain, I'd be hard pressed to call that a cyborg.