From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Cu'shan. (Blackness).  Habakkuk 3:7. Possibly the same as Cushan-Rishathaim, (Authorized Version, Chushan-rishathaim), king of Mesopotamia.  Judges 3:8;  Judges 3:10.

Morrish Bible Dictionary [2]

Perhaps Ethiopia, as in the margin,  Habakkuk 3:7; or it may refer to Chushan-rishathaim, the first recorded oppressor in the time of the judges.  Judges 3:8-10 .

Hastings' Dictionary of the Bible [3]

Cushan (  Habakkuk 3:7 ) = Arabian (?) Cush (wh. see).

Holman Bible Dictionary [4]

 Habakkuk 3:7 2 Chronicles 21:16

Easton's Bible Dictionary [5]

 Habakkuk 3:7 Judges 3:8,10

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [6]

(Heb. Kushan', כּוּשָׁן ).  ; Sept. Αἰθίοπες ; Vulg. Aethiopia ), usually regarded as a prolonged or poetic form ( Habakkuk 3:7) of the name of the land of CUSH (See Cush) (q.v.), but perhaps rather the same as Cushanrishtthain , (A.V. "Chushan-"), king of Mesopotamia ( Judges 3:8;  Judges 3:10). The order of events alluded to by the prophet seems to favor this supposition. First he appears to refer to former acts of divine favor ( Judges 3:2); he then speaks of the wonders at the giving of the Law, "God came from Teman, and the Holy One from Mount Paran;" and he adds, "I saw the tents of Cushan in affliction: [and] the tent-curtains of the land of Midian did tremble," as thou, h referring to the fear of the enemies of Israel at the manifestations of God's favor for his people. Chushan-rishathaim, the first recorded oppressor of the days of the Judges, may have been already reigning at the time of the entrance into Palestine. The Midianites, certainly allied with the Moabites at that time, feared the Israelites, and plotted against them (Numbers 22-25); and it is noticeable that Balaam was sent for from Aram ( Numbers 23:7), perhaps the Aram-naharaim of the oppressor. Habakkuk afterwards alludes to the crossing of Jordan or the Red Sea, or both ( Numbers 23:8-10;  Numbers 23:15), to the standing still of the sun and moon (11), and apparently to the destruction of the Canaanites (12, 13, 14) . Smith, s.v. There is, however, good reason for the supposition that Cushan here stands for an Asiatic Cush (see Meth. Quar. Rev. Jan. 1861, p. 81), as it is named in connection with Midian (q.v.). Delitzsch ( Der Prophet Habakuk , Leips. 1843, p. 159), who admits only the African Cush, holds that its mention along with Midian is intended to show how places so far removed from each other were equally affected by the theophany; but this is exceedingly strained, and at variance with the parallelism of the passage. (See Chushan-Rishathaim).

International Standard Bible Encyclopedia [7]

kūshan  : In the psalm of Habakkuk ( Habakkuk 3:7 ) "the tents of Cushan" are mentioned in an individualizing description of the effects of a theophany. Parallel is the phrase "the curtains of the land of Midian." Septuagint renders Cushan, כּוּשׁן , kūshān , by Αἰθιόπων , Aithiópōn , reading perhaps כּוּשׁים , kūshı̄m , or כּוּשׁין , kūshı̄n (כּוּשׁן , kūshin ). The context indicates that the same land or people is intended as the Old Testament elsewhere calls Cush, yet vaguely and not in any strict geographical usage that would limit it to Africa.