idiomatic \id`iomat"ic\, idiomatical \id`iomat"ical\, a.
   gr. 'idiwmatiko`s.
   1. of or pertaining to, or conforming to, the mode of
      expression peculiar to a language; as, an idiomatic
      meaning; an idiomatic phrase. -- id`iomat"ically,
      adv.
      1913 webster

   2. of or pertaining to, or of the nature of an idiom3;
      having a meaning that is peculiar to itself and not
      predictable from general rules.
      pjc
see also:
id`iomat"ically idiom 

idiomatical
     adj : of or relating to or conforming to idiom; "idiomatic
           english" syn: idiomatic
see also:
idiomatic