It's used in many words to describe something that is spiny, prickly, or bristly, like:
* Echinoderm: A group of marine animals with spiny skin, like starfish and sea urchins.
* Echinopsis: A genus of cacti with spiny stems.
* Echinate: Having spines or prickles.
The name "echino" itself often refers to the spiny shell of a sea urchin or other similar animals.