The Collaborative International Dictionary of English v.0.48:

Iota \I*o"ta\, n. [L., fr. Gr. 'iw^ta. See Jot.]
   [1913 Webster]
   1. The ninth letter of the Greek alphabet ([iota])
      corresponding with the English i.
      [1913 Webster]

   2. [from iota being the smallest letter in the Greek
      alphabet.] A very small quantity or degree; a jot; a
      particle.
      [1913 Webster +PJC]

            They never depart an iota from the authentic
            formulas of tyranny and usurpation.   --Burke.
      [1913 Webster]

   Iota subscript (Gr. Gram.), iota written beneath a
      preceding vowel, as a,, h,, w,, -- done when iota is
      silent.
      [1913 Webster]