The Collaborative International Dictionary of English v.0.48:
Rit \Rit\, obs. 3d pers. sing. pres. of Ride, contracted from rideth. --Chaucer. [1913 Webster]WordNet (r) 3.0 (2006):
rit. adj 1: gradually decreasing in tempo [syn: rallentando, ritardando, ritenuto, rit.]