That elusive state which is indefinable and uncontrollable but utterly desirable.
From the telegraph.co.uk
They spoke of some indefinable magic that championship teams almost always had.
From the chron.com
To put it another way, an indefinable aura of middleness is his greatest strength.
From the time.com
It may be an indefinable quality but all international fast bowlers need it.
From the independent.co.uk
All is taken as primitive and indefinable and the others are defined in terms of it.
From the en.wikipedia.org
From the core of the very stone on which Jesus lay an indefinable light pours forth.
From the en.wikipedia.org
Something was happening to me through this whole process that's indefinable.
From the sfgate.com
They can add an indefinable sprinkle of magic dust to the daily palette of offerings.
From the independent.co.uk
Star quality is supposed to be indefinable, but Bacall helps to define it.
From the time.com
More examples
Not capable of being precisely or readily described; not easily put into words; "an indefinable feeling of terror"; "an abstract concept that seems indefinable"
Defying expression or description; "indefinable yearnings"; "indescribable beauty"; "ineffable ecstasy"; "inexpressible anguish"; "unspeakable happiness"; "unutterable contempt"; "a thing of untellable splendor"
That cannot be precisely defined or put into words; That defies description; indescribable