• WordNet 3.6
    • adj acicular narrow and long and pointed; as pine leaves
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Webster's Revised Unabridged Dictionary
    • a Acicular Needle-shaped; slender like a needle or bristle, as some leaves or crystals; also, having sharp points like needles.
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Century Dictionary and Cyclopedia
    • acicular Having the shape of a slender needle or stout bristle; having a sharp point like a needle: as, an acicular prism, like those of stibnite; an acicular bill, as that of a humming-bird. Other forms are aciculate, aciculated, aciculiform, and aciculine.
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Chambers's Twentieth Century Dictionary
    • adj Acicular as-ik′ū-lar needle-shaped; slender and sharp-pointed
    • Acicular Also Acic′ulate, Acic′ulated
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In literature:

Soon Birdie and myself were a mass of acicular crystals; it was a true easterly fog.
"A Lady's Life in the Rocky Mountains" by Isabella L. Bird
The obelisk is from another of Nature's patterns; it is only a gigantic acicular crystal.
"Over the Teacups" by Oliver Wendell Holmes, Sr.
Hyoscyamine crystallizes in the acicular form, with greater difficulty even than atropine, it also forms less compact crystals.
"Scientific American Supplement, No. 324, March 18, 1882" by Various
Not far from the shore, I noticed, in a little ravine, a group of eight acicular-leaved trees.
"A Visit to the Holy Land, Egypt, and Italy" by Ida Pfeiffer
Soon Birdie and myself were a mass of acicular crystals; it was a true easterly fog.
"Celebrated Women Travellers of the Nineteenth Century" by W. H. Davenport Adams
The plumbago occurs both amorphous, and in long acicular crystals.
"In the Arctic Seas" by Francis Leopold McClintock

In science:

Such martensites are called acicular martensites.
Arrested States of Solids
Optical micrographs of acicular martensites reveal that the jammed plates lie along habit planes that criss-cross and partition the surrounding fcc (parent) matrix.
Arrested States of Solids
There have been similar suggestion in the literature, but as far as we know there has been no direct visualization studies of the microstructure of acicular martensites using optical micrographs.
Arrested States of Solids