Source : Webster's Revised Unabridged Dictionary (1913)

Acicula \A*cic"u*la\, n.; pl. {Acicul[ae]}. [L., a small needle,
   dimin. of acus needle.] (Nat. Hist.)
   One of the needlelike or bristlelike spines or prickles of
   some animals and plants; also, a needlelike crystal.

Source : WordNet®

acicula
     n : a needle-like part or structure of a plant or animal or
         crystal; as a spine or bristle or crystal
     [also: {aciculae} (pl)]

acicula
     See {aciculum}
     [also: {aciculae} (pl)]