The Collaborative International Dictionary
Sinistrorse
Sinistrorse \Sin"is*trorse`\, a. [See Sinistrolsal.] Turning to the left (of the spectator) in the ascending line; -- the opposite of dextrorse. See Dextrorse.
Douglas Harper's Etymology Dictionary
sinistrorse
1856, a word wanted by the botanists to describe the direction of spiral structures in nature, from Latin sinistrorsus "toward the left side," from sinister "left" (see sinister). It was paired with dextrorse but confusion over what was the proper point of view to reckon leftward or rightward spiraling prevented the word being as useful as it might have been.
Wiktionary
sinistrorse
a. Turning to the left (of the observer) in the ascending line.
WordNet
sinistrorse
adj. spiraling upward from right to left; "sinistrorse vines" [syn: sinistrorsal]