Headword and gloss are both aorist participles, in the feminine nominative singular; the headword one, unattested outside lexicography, is evidently quoted from somewhere (perhaps comedy).
The entry as a whole is an abbreviated (and slightly altered) version of Hesychius s.v. e)nplateia/sasa (sic): e)n platei/ais tu/ptousa tai=s xersi/n. h)\ trufereuome/nh. LSJ under the present headword quote this without venturing an English translation. The first part of one could presumably be '[she] striking with the flat(s) of the hands', a sense of the uncompound verb plateia/zw attested in Pherecrates fr. 224 Kock (now 258 K.-A.), but that is merely the first of three senses of it recognised by LSJ; for sense III, 'to be a braggart', see pi 1704. As to the part of Hesychius' gloss which the Suda does reproduce, it implies a fastidious luxury that would be effeminate in a man (but can scarcely incur that charge in a woman).