cut down, lament, mourn, (be-)wail

Boyd’s Bible Dictionary:

Very public and demonstrative
(Gen. 23:2; 37:29-35). Period, seven to seventy days (Gen. 1:3; 1 Sam. 31:13). Hired mourners (EccL 12:5; Matt. 9:23). Methods, weeping, tearing clothes, wearing sackcloth, sprinkling with ashes or dust, shaving head, plucking beard, fasting, laceration.

Concise Bible Dictionary:

It was the habit of the Hebrews, as it still is in the East, to make a great demonstration of their mourning. They would beat their breasts, cover their heads, fast, put dust and ashes on their heads, neglect their hair, wear dull-colored garments, rend their clothes, wear sackcloth, and so forth. For Asa and Zedekiah there was “great burning” of odors at their death, which was most probably copied from the heathen (2 Chron. 16:14; Jer. 34:5). At a death professional mourners were hired, mostly women. “Call for the mourning women.... let them make haste, and take up a wailing for us, that our eyes may run down with tears, and our eyelids gush out with waters” (Jer. 9:17-18; compare 2 Sam. 14:2; Amos 5:16). Musicians also attended at deaths, who played mournful strains (Matt. 9:23). God does not desire those who are bereaved to be without feeling: the Lord wept at the grave of Lazarus, but He would have reality in all things. He had to say to His people, “Rend your heart, and not your garments” (Joel 2:13).

Strong’s Dictionary of Greek Words:

Greek:
κόπτω
Transliteration:
kopto
Phonic:
kop’-to
Meaning:
a primary verb; to "chop"; specially, to beat the breast in grief
KJV Usage:
cut down, lament, mourn, (be-)wail. Compare the base of 5114

From Manners and Customs of the Bible:

Genesis 37:34. Jacob rent his clothes, and put sackcloth upon his loins, and mourned for his son many days.
Rending the clothes as a token of grief is a very ancient custom, and is often referred to in the Bible. See Joshua 7:6; 1 Samuel 4:12; 2 Samuel 1:11; 3:31; 13:31; 2 Kings 2:12; 18:37; 19:1; Ezra 9:3; Job 1:20. A Jewish writer, quoted by Brinier, says that this ceremony was performed in the following mariner: “They take a knife, and holding the blade downward, do give the upper garment a cut on the right side, and then rend it a hand’s breadth. This is done for the five following relations, brother, sister, son, daughter, or wife; but for father or mother the rent is on the left side, and in all the garments” (Oriental Customs, No. 65).
Sackcloth is also frequently mentioned. It was generally made of the hair of goats or of camels, and was coarse and black. It was used for straining liquids, for sacks, and for mourning garments. When used for mourning it was sometimes worn next to the skin, which it must have chafed by its harshness, and at other times it was hung like a sack over the outer garments, or instead of them. A girdle of similar material confined its loose folds. Ahab, on one occasion, appears to have worn sackcloth next to his skin all night. See 1 Kings 21:27. In Revelation 6:12, in the darkness accompanying an earthquake, the sun is said to have become as “black as sackcloth of hair.”