LSJ
ἡ, military standard, Plb. 2.32.6, LXX Is. 30.17, Mon. Anc. 15.23, 16.3. = Lat. vexillum, as a decoration, OGI 560.13 (Tlos, i AD).
a body of troops under one standard, the Roman manipulus, UPZ 14.23, al. (ii BC), Sammelb. 1436.10 (ii BC), Plb. 1.33.9, 3.113.3, 6.24.5, etc. ; cf. σημεῖον 1.4b.
image of Emperor on standard, J. BJ 2.9.2. = σῆμα 5 (on shield), Sch. Ar. Ra. 963. = σημεῖον, διαξέσας σημείας (on stone) IG 7.3073.138 (Lebadea). (The spellings σημεία as in IG l.c., UPZ 18.5 (ii BC), and good Mss. of Plb. (v. vol. 4 p. xxi B.-W.), D.H. 8.64, 9.13, al., D.S. 20.90, and σημέα as in UPZ 14.23, Sammelb. l.c., Mon. Anc. ll. cc., Abh.Berl.Akad. 1932 (5).41 (Pergam., ii AD), are prob. the only early spellings; σημαία which is found in Plu. Fab. 12 and as v.l. in Plb., D.H. 8.65, al., is prob. f.l. for σημέα.)
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
Pape
ἡ, = σημαία, Polyb., zw. L.
Pape, Griechisch-deutsches Handwörterbuch (3. Aufl., 1914)