Present participle form: the process of confusing someone or muddying their thinking.
From 'fuddle' plus the progressive suffix '-ing', which creates the continuous form of verbs and can also function as a gerund (noun) or adjective.
The '-ing' suffix is maybe the most flexible in English—it works as a verb form, a noun ('fuddling is confusing'), or an adjective ('a fuddling problem'), which is why linguists call it so productive.
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