Subjecting a system or element to a test, experiment, comparison, analysis, or the like, to determine quality, amount, acceptability, characteristics, correctness, compliance with requirements, etc. (Dictionary.com 2012)
Dictionary.com. 2012. "Prove." Available at http://dictionary.reference.com/browse/prove.
This definition is the gerund of the Dictionary.com definition. In systems engineering, proving a system generally consists of verification and validation.