[ 'ɒsɪk(ə)l ]
■ noun
1》 Anatomy & Zoology a very small bone, especially one of those in the middle ear.
2》 Zoology a small piece of calcified material forming part of the skeleton of an invertebrate animal such as an echinoderm.
Origin
C16: from L. ossiculum , dimin. of os 'bone'.