Be'athah means terror or sudden ruin — the state of being overwhelmed by sudden calamity. It derives from ba'ath (H1204), "to be terrified." The noun conveys not just the feeling of fear but the objective reality of devastating destruction that causes it.
Jeremiah uses be'athah to announce the terror coming upon Babylon as divine retribution (Jeremiah 50:38). The irony is profound: Babylon, which had been God's instrument of terror against Judah, will itself be consumed by terror. This reversal — the terrifier becoming the terrified — is a recurring pattern in prophetic judgment. God turns the weapons of the oppressor back upon themselves. The word serves as a warning that no empire is exempt from the moral order God has established.