The headword is a feminine noun in the nominative singular; see generally LSJ s.v. It is possibly generated by the quotation given, where it appears in the genitive singular, though perhaps more probably quoted from somewhere in its own right, e.g. Aristophanes, Acharnians 351 (cf. epsilon 2095, lambda 124, mu 196).
[1] Cuttlefish are not true fish, but are actually cephalopod marine molluscs of the order Sepiida; see Reid, et al., pp. 56ff. When alarmed, the cuttlefish secretes a defensive dark brown fluid, which is the origin of the English word sepia; see OED s.v. The headword is identically glossed by ps.-Herodian, Partitiones 125.8; cf. ps.-Zonaras 1639.7. Adler also cites Ambrosian Lexicon 260 and 278.
[2] Aristophanes, Ecclesiazusae [Assemblywomen] 554 (web address 1): Blepyrus sits Praxagora down before he tells the uninformed midwife that the city's governance has been handed over to its women. The Suda incorrectly transmits the masculine participle masw/menos (chewing) here; as it does pertain to Praxagora, the feminine participle maswme/nh is required. [In her critical apparatus Adler reports that mss GV read maso/menos, apparently a mistaken spelling.] Cuttlefish flesh is tender, is excellent for human consumption, remains a food item even today (Reid, et al., ibid.), and was indeed favored in ancient Greece, where its consumption was symbolic of a sumptuous life (Hickie, p. 644n5). But see further, next note.
[3] The scholia vetera to Ecclesiazusae 554 have oi(=on e)ntrufw=sa dia\ th\n e)cousi/an, 'as if she is reveling in ...'. The Suda changes the participle to trufw=n, i.e. the corresponding masculine of the uncompound verb. As to the value of the scholion in understanding Aristophanes' phrase, Ussher (pp. 151-2) is dubious: 'apart from the fact that it clearly is not literal ... Blepyrus' meaning is obscure'.