| Verb | 1. | flare up - ignite quickly and suddenly, especially after having died down; "the fire flared up and died down once again"ignite, light - cause to start burning; subject to fire or great heat; "Great heat can ignite almost any dry matter"; "Light a cigarette" kindle, inflame - catch fire; "The dried grass of the prairie kindled, spreading the flames for miles" | |
| 2. | flare up - erupt or intensify suddenly; "Unrest erupted in the country"; "Tempers flared at the meeting"; "The crowd irrupted into a burst of patriotism"deepen, intensify - become more intense; "The debate intensified"; "His dislike for raw fish only deepened in Japan" | |