Duchamp’s term for the all but imperceptible difference between two seemingly identical items was, the term infrathin [inframince], a term closely linked to what Duchamp also called deferral or delay. ...

Indeed, infrathin, Duchamp declared, cannot be defined, ‘One can only give examples of it.’

 

Marjorie Perloff, "But isn’t the same at least the same?”: Translatability in Wittgenstein, Duchamp, and Jacques Roubaud, in: JACKET # 14 - July 2001