Definition of ctenidium
plural ctenidia
\-ēə\
1
: the gill of a mollusk consisting typically of a respiratory structure that resembles a comb or feather, has a main stem with lateral lamellae, and is developed from the inner side of the mantle
—distinguished from ceras
2
: a structure consisting of a row of spines resembling the teeth of a comb on the head or thorax, or both, of certain fleas
