The Jets confirmed the trade, pending physicals for both players Tuesday.
The move reunites Hunter with former Jets offensive coordinator Brian Schottenheimer.
The move comes four days after the Jets benched Hunter. His replacement, Austin Howard, received positive reviews for his performance Sunday night against the Carolina Panthers, but the Jets wanted to fortify the weakest spot on their offensive line.
Smith, the second overall pick in 2009, lost his starting job to Barry Richardson, culminating a stunning downfall. After three seasons of injuries and ineffectiveness, the Rams finally decided to move on.
The writing was on the wall as far back as April, when Smith agreed to a massive pay cut, lowering his salary from $10 million to $4 million -- all guaranteed.
Hunter is owed $2.45 million guaranteed on his contract.
The Jets, under heavy criticism for not addressing the issue in the offseason, have reached the point of desperation. On the eve of training camp, they traded for former Panther Jeff Otah, another first-round disappointment, but the deal was voided a week later when Otah failed his physical.
At the start of camp, the Jets professed their faith in the beleaguered Hunter, but they ran out of patience after he allowed 2.5 sacks in an Aug. 18 loss to the New York Giants. Hunter, hounded by fan and media criticism, lost his confidence, leaving the Jets little choice but to bench him.
Hunter heard the insults from fans behind the Jets' bench and he had to be restrained by teammate Vladimir Ducasse from approaching them, according to a team source. The organization felt it would be difficult for Hunter, known for spiraling into mental funks, to continue in New York.
They turned to the unproven Howard, who didn't allow any sacks in the game.
"I thought Austin Howard had a nice game for us," Jets coach Rex Ryan said.
On Sunday night, Hunter played about 10 snaps as an extra blocker in two-tight end packages, returning to the role where he enjoyed success in 2010. But, in the fourth quarter, he allowed a sack at left tackle, hearing it once again from the fans.
The Jets and Rams have swapped draft busts in recent days. On Aug. 22, the Rams signed defensive end Vernon Gholston, whom the Jets drafted sixth overall in 2008.
In 2009, the Rams made Smith the second pick, three spots ahead of where the Jets drafted quarterback Mark Sanchez. At the time, the Jets were concerned because they thought there was a chance the Rams were going to pick Sanchez.
Concussions have limited Smith to only 29 games (26 starts) over three seasons. The former Baylor standout suffered a severe concussion as a rookie.
