Acicula

noun

1. A slender, needlelike part or structure, such as a spine or bristle of certain plants and animals or a crystal of certain minerals.
2. In botany: The bristle-like prolongation of the rachilla of a grass-spike.
3. A tooth-like process in the hymenium of certain fungi.
4. Plural of aciculum.
5. A needle, pin, or bodkin, of wood or bone, used by Roman women as a hair-pin. It was not smaller than an acus (which see), but of inferior material.