Source : Webster's Revised Unabridged Dictionary (1913)

Os \Os\, n.; pl. {Osar}. [Sw. [*a]s ridge, chain of hills, pl.
   [*a]sar.] (Geol.)
   One of the ridges of sand or gravel found in Sweden, etc.,
   supposed by some to be of marine origin, but probably formed
   by subglacial waters. The osar are similar to the kames of
   Scotland and the eschars of Ireland. See {Eschar}.

Osar \O"sar\, n. pl. (Geol.)
   See 3d {Os}.

Source : WordNet®

os
     n 1: a mouth or mouthlike opening
     2: a hard brittle blue-gray or blue-black metallic element that
        is one of the platinum metals; the heaviest metal known
        [syn: {osmium}, {atomic number 76}]
     3: (computer science) software that controls the execution of
        computer programs and may provide various services [syn: {operating
        system}]
     4: the left eye [syn: {oculus sinister}]
     5: rigid connective tissue that makes up the skeleton of
        vertebrates [syn: {bone}]
     [also: {ossa} (pl), {osar} (pl), {ora} (pl)]

osar
     See {os}