How do you differentiate between a transitive verb and a noun?

You might like to tell your fellow team member that the Oxford English Dictionary records parsing as having been used as a noun since the sixteenth century.

The noun form of parse is, well, parse. NOAD gives the following description:

Computing: an act of or the result obtained by parsing a string or a text.

So how do you use parsing as a noun? The gerund form of a verb could be used as a noun. Here are some examples:

Run: (runs, running ; past ran |ran|; past participle run). Noun: Run.

So you could say a cross country run. Or

Running keeps you healthy. Here running is used as a noun. Or

Parsing is a common term used in psycholinguistics when describing language comprehension.(Wikipedia)