The Collaborative International Dictionary of English v.0.48:
Sinistrorsal \Sin`is*tror"sal\, a. [L. sinistrorsus, sinistroversus, turned toward the left side; sinister left + vertere, vortere, versum, vorsum, to turn.] Rising spirally from right to left (of the spectator); sinistrorse. [1913 Webster]WordNet (r) 3.0 (2006):
sinistrorsal adj 1: spiraling upward from right to left; "sinistrorse vines" [syn: sinistrorse, sinistrorsal]