Meaning: not capable of being precisely or readily described; not easily put into words; "an indefinable feeling of terror"; "an abstract concept that seems indefinable"
It's not the features, but something indefinable. He's a second von Sohn.
Of course that is something indefinable, impalpable, but it has never been so before, and that glance means a great deal," she thought.
Lastly, if from a single point there be conceived to be drawn two diverging lines which at first are at a definite distance apart, but are produced to infinity, it is certain that the distance between the two lines will be continually increased, until at length it changes from definite to indefinable.
From that my thoughts went to the indefinable queerness of the deformed man on the beach. I never saw such a gait, such odd motions as he pulled at the box. I recalled that none of these men had spoken to me, though most of them I had found looking at me at one time or another in a peculiarly furtive manner, quite unlike the frank stare of your unsophisticated savage.