[ ɪm'pɛnɪtrəb(ə)l ]
■ adjective
1》 impossible to pass through or enter.
2》 impossible to understand.
3》 Physics (of matter) incapable of occupying the same space as other matter at the same time.
Derivatives
impenetrability noun
impenetrably adverb
Origin
ME: via Fr. from L. impenetrabilis , from in- 'not' + penetrabilis 'able to be pierced', from penetrare (see penetrate ).