The headword is aorist active participle, neuter singular nominative or accusative, of the verb prosrh/gnumi. In literature prior to the Suda it is only attested in John Chrysostom's Commentary on Psalm 145 (PG 55.519), concerning a ship crashing against rocks. (Hesychius pi3679 presents different forms of the same verbs as headword and gloss, but in the opposite order.)
Adler ascribes this entry to the source of the Lexicon Ambrosianum.