Lexical Definition

‎φαντάζω‎ phantázō (fan-tad'-zo) to make visible ^G:V
from a derivative of ‎φαίνω‎

sight.

• to make apparent, i.e. (passively) to appear (neuter participle as noun, a spectacle)

Abbott-Smith

** φαντάζω (< φαίνω) [in LXX: Wi 6:16, Si 31 (34):5* ;]
to make visible. In cl. used in pass. only, = φαίνομαι, to become visible, appear: ptcp., He 12:21.†

Abbott-Smith References

Liddell-Scott-Jones

φαντάζω,

(φαίνω) make visible, present to the eye or mind, τι [Refs 3rd c.AD+] deceive, [Refs 4th c.AD+]:—middle, with aorist passive, place before one's mind, picture an object to oneself, imagine, τι [Refs 5th c.BC+]; fancy, imagine, ὅτι.. [Refs 5th c.BC+]; τοῖς μηδὲ φαντασθεῖσιν ὡς καλόν.. [Refs 3rd c.AD+]; with accusative and infinitive, [Refs 4th c.AD+]

__II in early writers only in passive, future φαντασθήσομαι [Refs 5th c.BC+]: aorist ἐφαντάσθην [Refs]:— become visible, appear, σφι [Refs 5th c.BC+]; also, to be heard, μυκαὶ σηκοῖς ἔνι φ. [NT+3rd c.BC+]
__II.b to be terrified by visions or phantasms, [Refs]
__II.2 make a show, [Refs 5th c.BC+]
__II.3 φαντάζεσθαί τινι make oneself like someone, take his form, φανταζόμενος.. γυναικί [Refs 4th c.BC+]
__II.4 appear so and so, to be imagined, [Refs 5th c.BC+]
__II.5 com. for συκοφαντεῖσθαι, to be informed against, [Refs 5th c.BC+]

_{LSJ Scripture Refs: Heb.12.21}