Merriam-Webster Collegiate Dictionary - smolder

 or smoulder  intransitive verb  (~ed or smouldered; ~ing or smouldering)  Etymology: Middle English ~en to smother, from ~ smoke, smudge; akin to Middle Dutch smolen to ~  Date: 1529  1.  a. to burn sluggishly, without flame, and often with much smoke  b. to be consumed by ~ing — often used with out  2. to exist in a state of suppressed activity hostilities ~ed for years  3. to show suppressed anger, hate, or jealousy eyes ~ing with hate