Ostensive definition: Defining a term by indicating an exemplary or paradigmatic
referent. I say to my Spanish friend, ‘What is a lápiz?’; he points to a pencil and
says, ‘This is a lápiz.’ That would be an ostensive definition of ‘lápiz’.
 

See:
(1) Merriam-Webster Dictionary entry (meaning 2).
(2) Ludwig Wittgenstein, Philosophical Investigations, §32.