From haphak; a destruction -- when...overthrew, overthrow(-n).
see HEBREW haphak
H4114. mahpekah
[מַהְמֵּכָה] noun feminine overthrow — always construct מַהְמֵּכַת; & always of overthrow of Sodom, Gomorrah etc., except Isaiah 1:7 ׳מ זָרִים, where read סְדֹם (Ew Che RSProph. 345 Di and others; also LagSemitic i. 3); yet even so probably gloss, compare StuJPTh 1877, 714; ׳מ סְדֹם Deuteronomy 29:22; Jeremiah 49:18; and with force of verbal noun, governing accusative, ׳מ אתסֿדם אלהים Isaiah 13:19; Jeremiah 50:40; Amos 4:11. compare also הָפַךְ 1b, הֲפֵכָה.