πτιστέον
From LSJ
Περὶ τοῦ ἐπέκεινα τοῦ νοῦ κατὰ μὲν νόησιν πολλὰ λέγεται, θεωρεῖται δὲ ἀνοησίᾳ κρείττονι νοήσεως → On the subject of that which is beyond intellect, many statements are made on the basis of intellection, but it may be immediately cognised only by means of a non-intellection superior to intellection
English (LSJ)
one must winnow, ζειάς, σῖτον, Gp.3.7.1,8.
Greek (Liddell-Scott)
πτιστέον: ῥημ. ἐπίθ. τοῦ πτίσσω, δεῖ πτίσσειν, Γεωπ. 3. 7, 1.