Source : Webster's Revised Unabridged Dictionary (1913)

Sinistrorse \Sin"is*trorse`\, a. [See {Sinistrolsal}.]
   Turning to the left (of the spectator) in the ascending line;
   -- the opposite of dextrorse. See {Dextrorse}.

Source : WordNet®

sinistrorse
     adj : spiraling upward from right to left; "sinistrorse vines"
           [syn: {sinistrorsal}]