fire·fly 
(fīrflī′)
(fīrflī′)n.
Any of various nocturnal beetles of the family Lampyridae, characteristically having bioluminescent organs in the tip of the abdomen that produce a flashing light. Also called lightning bug.
- fall to pieces
- Fallujah
- fall upon
- false
- false alarm
- false arrest
- false color
- false-color
- false consciousness
- false face
- false friend
- false fruit
- false-hearted
- false-heartedness
- false hellebore
- falsehood
- false imprisonment
- false indigo
- falsely
- false memory
- false-memory syndrome
- false negative
- false-negative
- falseness
- false positive