threequel 
noun
The third film, book, etc. in a series; a second sequel.In 1977, the opening crawl of Star Wars - announcing the film as ‘Episode IV: A New Hope ‘- stoked an endless stream of sequels, threequels and prequels.
Origin
1980s: from three + sequel.
- Prince Royal
- Prince Rupert's drop
- Prince Rupert's Land
- prince's feather
- princeship
- Princes in the Tower
- Prince's metal
- Princes' metal
- prince's mixture
- prince's pine
- princess
- princess cut
- princessdom
- princesse lointaine
- princessly
- princess of the blood
- princess palatine
- princess phone
- Princess Regent
- princess-ring
- Princess Royal
- princess-ship
- princess telephone
- princess tree
- prince's stuff