The roster moves came four days after the Ravens lost Tavon Young to a torn ACL. Boykin has primarily played nickelback, the role Young was expected to fill.
The Ravens also signed cornerback Al-Hajj Shabazz.
Terminating Arrington's contract frees up approximately $2.1 million in cap space.
Arrington, 30, has not appeared in a game since the 2015 season. He missed the entire 2016 season because of a concussion and was entering the final year of a three-year contract with the Ravens. He was released with a failed physical designation.
Shabazz, 24, appeared in eight games last season with the Steelers and Texans. He made one tackle.
Baltimore's other options to replace Young included Lardarius Webb, who switched from corner to safety last season; Maurice Canady, who has not played a defensive snap in the regular season; and Arrington.