ff or ff.

1. Fecerunt (Latin), (they) did it or made it
2. Folios (printing)
3. Following pages, lines, etc
4. Fortissimo (music)

FF

1. Form feed (computing)
2. French franc or francs

• heat pump
• heat pumps
• heat-resistant
• heats
• heat-seeking
• heat shield
• heat shields
• heat sink
• heat sinks
• heatspot
• heatspots
• heatstroke
• heatstrokes
• heat treatment
• heatwave
• heaume
• heaumes
• heave
• heaved
• heave ho
• heave-ho
• innocency
• innocent
• innocently
• innocents