acorn barnacle

noun

1. See under barnacle¹(def 1).

noun

1. any marine crustacean of the subclass Cirripedia, usually having a calcareous shell, being either stalked (goose barnacle) and attaching itself to ship bottoms and floating timber, or stalkless (rock barnacle or acorn barnacle) and attaching itself to rocks, especially in the intertidal zone.
2. a person or thing that clings tenaciously.

noun

1. any of various marine crustaceans of the subclass Cirripedia that, as adults, live attached to rocks, ship bottoms, etc. They have feathery food-catching cirri protruding from a hard shellSee acorn barnacle, goose barnacle
2. a person or thing that is difficult to get rid of

noun

1. any of various barnacles, such as Balanus balanoides, that live attached to rocks and have a volcano-shaped shell from the top of which protrude feathery food-catching appendages (cirri)

n.

early 13c., “species of wild goose;” as a type of “shellfish,” first recorded 1580s. Often derived from a Celtic source (cf. Breton bernik, a kind of shellfish), but the application to the goose predates that of the shellfish in English. The goose nests in the Arctic in summer and returns to Europe in the winter, hence the mystery surrounding its reproduction. It was believed in ancient superstition to hatch from barnacle’s shell, possibly because the crustacean’s feathery stalks resemble goose down. The scientific name of the crustacean, Cirripedes, is from Greek cirri “curls of hair” + pedes “feet.”

1. Any of various small marine crustaceans of the subclass Cirripedia that form a hard shell in the adult stage and attach themselves to underwater surfaces, such as rocks, the bottoms of ships, and the skin of whales.