Lexical Definition

‎καθαίρω‎ kathaírō (kath-ah'-ee-ro) to prune ^G:V
from ‎καθαρός‎

purge.

• to cleanse, i.e. (specially) to prune
• figuratively, to expiate

Abbott-Smith

καθαίρω (< καθαρός), [in LXX: Is 28:27 (דּוּשׁ ho.), II Ki 4:6, Je 51:39 א* ;]
to cleanse: of pruning, Jo 15:2 (cf. καθαρίζω).†

Abbott-Smith References

Liddell-Scott-Jones

καθαίρω,

future κᾰθᾰρῶ [Refs 5th c.BC+]: aorist 1 ἐκάθηρα [Refs 8th c.BC+]; ἐκάθᾱρα is found in codices of [Refs 5th c.BC+], and commonly in later Gr., [Refs 4th c.BC+]; see below middle: perfect κεκάθαρκα (ἐκ-) [Refs 5th c.BC+]:— middle, future καθαροῦμαι [Refs 5th c.BC+]: aorist ἐκαθηράμην [Refs 5th c.BC+]; later ἐκαθᾱράμην [Refs 4th c.BC+]: passive, future καθαρθήσομαι [Refs 2nd c.AD+]: aorist ἐκαθάρθην [Refs 5th c.BC+] is falsa lectio in [Refs 2nd c.AD+]: perfect κεκάθαρμαι [Refs 5th c.BC+]: (καθαρός):

__I cleanse, of things, καθήρατε δὲ κρητῆρας [Refs 8th c.BC+] [prev. cited]; of wounds, [Refs 5th c.BC+]; γῆν clear of weeds,[Refs 3rd c.BC+], etc.; χρυσόν purify, refine, [Refs 5th c.BC+]: metaphorically, purge, clear a land of monsters and robbers, [Refs 5th c.BC+]:—passive, τὴν νηδὺν ἀνασχισθεῖσαν καὶ καθαρθεῖσαν [Refs 5th c.BC+]
__I.2 in religious sense, purify, [δέπας] ἐκάθηρε θεείῳ by fumigating with sulphur, [Refs 8th c.BC+]; κ. τινὰ φόνου purify him from blood, [Refs 5th c.BC+]; Δῆλον κ. [Refs 5th c.BC+]; στόλον κ., Latin classem lustrare, [Refs 1st c.BC+]:— middle, purify oneself, get purified, [Refs 5th c.BC+]; καθήρασθαι στόμα keep one's tongue pure, [Refs 4th c.BC+]:—passive, κεκαθαρμένος καὶ τετελεσμένος [Refs 5th c.BC+]
__I.3 in Medicine texts, purge, evacuate, either by purgatives or emetics, κ. κάτω ἢ ἄνω [Refs 5th c.BC+]:—middle, κατὰ κύστιν ἐκαθήρατο [Refs 5th c.BC+] —passive [Refs], etc.; also of menstruation, [Refs]; of the after-birth, τὰ λοχεῖα κ. [Refs]; καθαίρων, ὁ, name for ἶρις, Ps.-[Refs 1st c.AD+]
__I.4 prune a tree,i.e.clear it of superfluous wood, [NT]
__I.5 sift, winnow grain, [Refs 2nd c.AD+]
__I.6 metaphorically, ={μαστιγόω}, [Refs 3rd c.BC+]
__II of the thing removed by purification, purge away, wash off, λύματα πάντα κάθηρεν [Refs 8th c.BC+]; clear away, τὰ λῃστικά [Refs 4th c.BC+]; also perhaps, clear up, explain an action, τὴν σύστασιν [Refs 4th c.BC+]
__III with double accusative, αἷμα κάθηρον.. Σαρπηδόνα cleanse him of blood, wash the blood off him, [Refs 8th c.BC+] —passive, καθαίρομαι γῆρας I am purged of old age, [Refs 5th c.BC+]

_{LSJ Scripture Refs: John.15.2}