Smolder is the American spelling of smoulder; the British write it with the ou. Either way it is the same verb, and it means to burn slowly with no flame — just heat, a red glow and a thin line of smoke. A cigarette left in an ashtray smolders. So do the ashes of a fire the next morning, and a mattress that a spark landed on hours ago. That last one matters: firefighters worry about smoldering because something can smolder unseen for a long time and then suddenly burst into flame. The second use is about feelings, and it is the one you meet most in books. Anger, resentment and hatred smolder — they stay hot inside a person without breaking out, sometimes for years. "His anger smoldered all through the meeting." There is also a warmer version used about attraction: a smoldering look, or a film star described as smoldering, means a dark, intense, held-back sexual heat. That sense is now half a joke in magazines, so use it carefully. As a noun, smolder is far less common than the verb, but it exists — the smolder of a fire, or the smolder in someone's eyes.

悶燒、陰燃（無火焰地慢慢燒）；（情緒）鬱積、暗自燃燒；（眼神）帶著壓抑的熱度