limpet

As a noun limpet

is a small mollusc, of the family Patellidae with a conical shell found clinging to rocks in the intertidal zones of rocky shores.

As an adjective limpetlike is

resembling or characteristic of a limpet.

As nouns the difference between limpet and barnacle

is that limpet is a small mollusc, of the family Patellidae with a conical shell found clinging to rocks in the intertidal zones of rocky shores while barnacle is a marine crustacean of the subclass Cirripedia that attaches itself to submerged surfaces such as tidal rocks or the bottoms of ships.

As a verb barnacle is

to connect with or attach.