From Longman Dictionary of Contemporary Englishmolluscmol‧lusc British English, mollusk American English /ˈmɒləsk $ ˈmɑː-/ noun [countable] 
HBAa type of sea or land animal that has a soft body covered by a hard shell snails and other molluscs —molluscan /məˈlʌskən/ adjective molluscan prey
HBAa type of sea or land animal that has a soft body covered by a hard shell snails and other molluscs —molluscan /məˈlʌskən/ adjective molluscan preyExamples from the Corpus
mollusc• I pictured my navel, soft and curled like a mollusc.• The typical life cycle is indirect, and the intermediate host is usually a mollusc.• A mollusc past the initial stages of growth increases in size without significantly changing the orientation and relative proportions of its organs.• This humble mollusc can be unreservedly recommended as it is hardy and lives exclusively on algae.• The fossil record is silent on this transition, but the earlier stages of mollusc evolution are becoming clear.• There are two types of mollusc that are actively venomous: the cone shells and the blue-ringed octopus.• It is a small mollusc, the size of a mussel, that starts life as a tiny free-swimming speck of jelly.• This symmetry is required basically for optimum structural strength and to suitably accommodate the mollusc it protects. 