Boyd’s Bible Dictionary:
(winnower). Winnowing shovel or fork used to throw chaff up into the wind, to separate it from the kernels (Isa. 30:24; Matt. 3:12).
Concise Bible Dictionary:
The fan was a small shovel, by which a portion of wheat was thrown up into the air, that the wind might carry away the chaff (Isa. 30:24; Jer. 4:11). It is also used symbolically for the judgments of God (Isa. 41:16; Jer. 15:7; Jer. 51:2); and for the discriminating power of the testimony of the Lord Jesus (Matt. 3:12; Luke 3:17).
Winnowing at Gezer