Definitions

1. adjective

relating to the heart or the heart-shaped organ in invertebrates such as mollusks and annelids.

“The cardiacea system in octopuses helps them detect vibrations in the water.”

2. noun

a class of invertebrates, including mollusks, annelids, and others, that have a heart-shaped organ.

“The cardiacea phylum includes a wide variety of species, from squids to earthworms.”