The headword is a Hebrew word (on which see also sigma 241) treated as indeclinable in Greek. However, the first three glosses here are either definitely or possibly accusative plural, so probably derive from commentary to a passage where the word functions as an accusative -- hence not from the Septuagint, where the only two attestations are nominative (Isaiah 6:2, see n. 2 below) and genitive (Isaiah 6:6). The supplementary glossing is in the nominative singular.
[1] = Synagoge sigma23 (s.v. sarafi/m) and Photius, Lexicon sigma78 Theodoridis (s.v. sa/rafin). Cunningham (on the Synagoge) also reports the presence of the same glosses in a number of mss of the Lexicon Cyrillianum. For more on the history of these glosses, see n. 2 below.
[2] Four of these five glosses (all except 'fiery mouths') occur in ps.-Dionysius the Areopagite 7.1 (also in Catena in epistulam ad Romanos (typus Monacensis) 293.13) where they purport to translate the Hebrew meaning of the words seraphim ('firebrands' and 'warmth bringers') and cherubim ('propagation...' and 'diffusion...', with plh=qos ('plenitude') in place of plhqusmo/s ('propagation')). An earlier text, however, Cyril of Alexandria PG 68.601.24, offers the last two as meanings for seraphim, as does the Suda and Hesychius sigma195 (s.v. sarafi/n), which Latte interprets as deriving from commentary to Isaiah 6:2 LXX (where the headword functions as a nominative plural). The gloss 'fiery mouths' is first found in John Chrysostom in his commentary on Isaiah and in his On the Incomprehensible Nature of God 3.330; in the latter of these texts he defines the Hebrew meaning of seraphim שׂרפים as "fiery mouths" and cherubim כּרובים as "propagated knowledge" (peplhqusme/nh gnw=sis). For references to further parallels see Theodoridis' apparatus fontium at Photius sigma78.