The firefighters managed to put out the blaze, but the embers could re-ignite it.

re-ignite 由前缀 re-（表示"再次"）和动词 ignite（点燃）组成。前缀 re- 表示重复或再次的动作，ignite 意为"点燃、引发"。re-ignite 合起来表示"重新点燃、再次引发"的意思。