To do with showing. Cf. ostentatious
Ludwig Wittgenstein wrote quite a bit about ostensive definition, which is 'simply' defining words by pointing to the things they stand for, just as you might go round the park with a toddler, naming things.
Wittgenstein's beef was with the elevation of this convenient pedagogical device to a totalistic theory of meaning which insisted that meaning consists in a sentence having something 'at the end of it' that it 'points' to. He has several criticisms of this, such as
'That is called "two"' -- pointing to two nuts -- is perfectly exact. But how can two be defined like that? The person one gives the definition to doesn't know what one wants to call "two"; he will suppose that "two" is the name given to this group of nuts! [...] when I want to assign a name to this group of nuts, he might understand it as a numeral.
Wittgenstein's 'slab' language-games are designed to show, inter alia, the possibility of constructing a language without simple ostensive definitions, as all the sentences are in the imperative, and have no denotation.