Adomah, 32, joined Forest from Aston Villa on a free transfer last summer.
But the Ghana international has made only five starts for the Championship club this season, featuring mostly as a substitute.
Adomah had largely been restricted to a substitutes’ role for the Reds, with 19 of his 27 appearances in the Garibaldi coming from off the bench.
He scored three times for the club, all of them coming back in August