Concise Bible Dictionary:
An agricultural instrument that needed sharpening: some suppose that the word signifies a plowshare; others, a mattock (1 Sam. 13:20-21).
Plow and Plowshare
Strong’s Dictionary of Hebrew Words:
Meaning:
of uncertain derivation; a hoe or other digging implement
KJV Usage:
coulter, plowshare
From Manners and Customs of the Bible:
Isaiah 2:4. They shall beat their swords into plowshares.
See also Joel 3:10, and Micah 4:3. in the passage in Joel the expression is reversed: “Beat your plowshares into swords.” Commentators are divided as to the meaning of ittim, variously rendering it “plowshares,” “spades,” “hoes,” “mattocks.” The word refers to instruments for stirring up the soil in some way, and, so far as concerns capability of conversion to swords, these may as well have been plowshares as anything else. The plowshare was a small piece of iron, which somewhat resembled a short sword, and might easily have been beaten into one, and with equal facility a sword could have been changed into a plowshare.