smolder

Short definition from Wiktionary

Verb

1. 1
   To burn with no flame and little smoke.
2. 2
   To show signs of repressed anger or suppressed mental turmoil or other strong emotion, such as passion.
3. 3
   To exist in a suppressed or hidden state.

Noun

1. 1
   The act of smoldering or something that smolders.