Source : Webster's Revised Unabridged Dictionary (1913)

Uncial \Un"cial\, a. [L. uncialis amounting to the twelfth part
   of a pound or a foot, from uncia the twelfth part of a pound
   or of a foot, an ounce, an inch: cf. F. oncial. See {Inch} a
   measure.]
   Of, pertaining to, or designating, a certain style of letters
   used in ancient manuscripts, esp. in Greek and Latin
   manuscripts. The letters are somewhat rounded, and the
   upstrokes and downstrokes usually have a slight inclination.
   These letters were used as early as the 1st century b. c.,
   and were seldom used after the 10th century a. d., being
   superseded by the cursive style.

Uncial \Un"cial\, n.
   An uncial letter.

Source : WordNet®

uncial
     adj : relating to or written in majuscule letters (which resemble
           modern capitals); "uncial letters"
     n : a style of orthography characterized by somewhat rounded
         capital letters; found especially in Greek and Latin
         manuscripts of the 4th to 8th centuries