俨然 is a literary word with two distinct uses. As an adjective it describes a solemn, dignified appearance or a neatly arranged state (e.g., 屋舍俨然 'houses are neatly arranged'). As an adverb it means 'just like' or 'as if', used to say someone or something looks exactly like something else, often with a slightly exaggerated or ironic tone (e.g., 俨然一副专家模样 'looking just like an expert'). It is not a verb; the POS label 'v.p.' in the source is likely a misclassification.