spiculum

Meanings

1. A thrusting javelin used by Romans that replaced the pilum in the late 3rd century.
2. A sharp, pointed crystal, especially of ice.
3. A sharp, needle-like structure, especially those making up the skeleton of a sponge.
4. A small radial emission of gas seen in the chromosphere and corona of the sun.

Etymology

From Latin spīculum (“a little sharp point”), from spīcum, alternative form of spīca (“point, spike”).