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.
the GNU version of the Collaborative International Dictionary of English
adjective.
Needle-shaped; slender like a needle or bristle, as some leaves or crystals; also, having sharp points like needles.