Source : Webster's Revised Unabridged Dictionary (1913)

Smoldering \Smol"der*ing\, Smouldering \Smoul"der*ing\, a.
   Being in a state of suppressed activity; quiet but not dead.

         Some evil chance Will make the smoldering scandal break
         and blaze.                               --Tennyson.

Smolder \Smol"der\, Smoulder \Smoul"der\, v. i. [imp. & p. p.
   {Smoldered}or {Smouldered}; p. pr. & vb. n. {Smoldering} or
   {Smouldering}.] [OE. smolderen; cf. Prov. G. sm["o]len,
   smelen, D. smeulen. Cf. {Smell}.]
   1. To burn and smoke without flame; to waste away by a slow
      and supressed combustion.

            The smoldering dust did round about him smoke.
                                                  --Spenser.

   2. To exist in a state of suppressed or smothered activity;
      to burn inwardly; as, a smoldering feud.

Source : WordNet®

smoldering
     adj 1: burning slowly without flame; "smoldering embers" [syn: {smouldering}]
     2: showing scarcely suppressed anger; "her tone
        was...conversational although...her eyes were smoldering"-
        James Hensel [syn: {smouldering}]