COUCH. A piece of furniture for reclining. The couch became so ornate that Amos rebuked the rich for the costly display of their couches (Amos.6.4). Sometimes, however, the couch was no more than a rolled-up mat that could be easily transported (Matt.9.6). See also Bed.
International Standard Bible Encyclopedia (1915)
Couch (verb): rabhats, "to crouch," "lurk," as a beast in readiness to spring on its prey. "If thou doest not well, sin coucheth at the door" (Ge 4:7, the King James Version "lieth"), waiting for it to open. Cain is warned to beware of the first temptations to evil, in his case especially a sullen and jealous disposition (compare Dante, Inferno, I, 30). See Abel; Cain. The tribe of Judah is compared for its bravery to a recumbent lion or lioness (Ge 49:9; compare Nu 24:9 f); and Issachar to "a strong ass, couching down between the sheepfolds" (Ge 49:14, the King James Version "between two burdens"; compare Jud 5:16). "The deep that coucheth beneath" (De 33:13), probably the springs of water, or possibly, as Driver suggests, "the subterranean deep, pictured as a gigantic monster."