What does "subtle" mean?

Subtle: Cunningly devised; crafty; treacherous; as, a subtle stratagem.

Additional senses

  1. 2.Characterized by refinement and niceness in drawing distinctions; nicely discriminating; -- said of persons; as, a subtle logician; refined; tenuous; sinuous; insinuating; hence, penetrative or pervasive; -- said of the mind; its faculties, or its operations; as, a subtle intellect; a subtle imagination; a subtle process of thought; also, difficult of apprehension; elusive. Things remote from use, obscure and subtle. Milton.
  2. 3.Smooth and deceptive. [Obs.] Like to a bowl upon a subtle ground [bowling ground]. Shak. Subtle is the most comprehensive of these epithets and implies the finest intellectual quality. See Shrewd, and Cunning.

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