noun

1. Astron. any of the short-lived, bright, dense gas jets continuously spurting up through the chromosphere of the sun: thought to be extensions of the photosphere's granules
2. Bot. a small spike; spikelet
3. Zool. a small, hard, needlelike piece or process, esp. of bony or calcareous material, as in the skeleton of the sponge

Etymology: < ModL & L: ModL spicula < ML, head of a lance or arrow < L spiculum, dim. of spica, a point, ear, spike