aura: a sensation (as of a cold breeze or bright light) that precedes the onset of certain disorders such as a migraine attack or epileptic seizure
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease
gunpowder: a mixture of potassium nitrate, charcoal, and sulfur in a 75:15:10 ratio which is used in gunnery, time fuses, and fireworks