Indefinable

It was in mid-summer, when the alchemy of Nature transmutes the sylvan landscape to one vivid and almost homogeneous mass of green; when the senses are well-nigh intoxicated with the surging seas of moist verdure and the subtly indefinable odours of the soil and the vegetation.

What I’m getting at is that Zamenhof not only built a linguistic object, but that behind that was an idea — an idea of brotherhood, a pacifist idea. That strength of an ideal — for which Esperantists were even persecuted under Nazism and Stalinism — is still conserved by the community of Esperantists. One cannot say that it has failed, but one thing needs to be said: the reason why any language is successful is always indefinable.

Love gives sensations that are often indefinable.

African tourism is changing, say travel industry leaders, moving away from the traditional safaris and packaged tours and towards the intimate, indefinable, infinitely Instagrammable lure of “experiences.”

The indefinable pulpy mass I found in the pocket of my freshly washed trousers had once been the stamps I was going to give to Tom for his stamp collection.

They apparently have a theory that the indefinable psychic gift that they call magic, and which we might designate "psychicism", can be acquired by accosting the soul of a murdered man in a burial ground at midnight.