The Collaborative International Dictionary of English v.0.48:

Rack \Rack\, v. i. [imp. & p. p. Racked (r[a^]kt); p. pr. &
   vb. n. Racking.] [See Rack that which stretches, or
   Rock, v.]
   To amble fast, causing a rocking or swaying motion of the
   body; to pace; -- said of a horse. --Fuller.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "racked":
   affected, afflicted, agonized, clawed, convulsed, crucified,
   devoured by, distressed, harrowed, hurt, hurting, imbued with,
   impressed, impressed with, in distress, in pain, lacerated,
   lancinated, martyred, martyrized, moved, obsessed, obsessed by,
   on the rack, pained, penetrated with, ripped, savaged, seized with,
   stricken, suffering, tormented, torn, tortured, touched, twisted,
   under the harrow, wounded, wracked, wrung