Awareness of & a conscious disregard of a substantial & unjustifiable risk that a result will occur or that a circumstance exists. The risk must be of such nature & degree that disregarding it constitutes a gross deviation from the standard of care that a reasonable person would observe in the situation.

Example
Intentionally: Pushing someone over intending that they fall onto the sharp rocks behind them & be killed or suffer serious physical injury
Knowingly: Pushing someone over knowing that there are sharp rocks behind them & knowing that falling on them could kill or cause them serious physical injury, but not intending harm to come to them
Recklessly: Pushing someone over knowing that there are sharp rocks behind them but not considering they could kill or cause them serious physical injury even though a reasonable person would recognize and be aware of the obvious risk
With Criminal Negligence: Pushing someone over towards the sharp rocks behind them without being aware of the rocks and obvious risk that the fall could kill or cause them serious physical injury even though a reasonable person would recognize and be aware of the obvious risk