Present participle of expertise used as a verb (British usage); providing expert opinion or assessment on something.
From expertise (noun) + -ing (present participle/gerund suffix). The British English verb 'expertise' creates 'expertising' as its -ing form. This represents the British convention of turning the noun 'expertise' into a verb, while American English more commonly uses 'expertize.'
If you're British and you say you're 'expertising' a document, you're using a verb form most Americans wouldn't naturally use—it's a great example of how the same noun gets verbed differently across English-speaking countries!
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