cen·ter·board 
(sĕntər-bôrd′)
(sĕntər-bôrd′)n.
A movable keel in a sailboat that can be pivoted upward to reduce the boat's draft in shallow water.
- aporia
- aport
- aposematic coloration
- aposiopesis
- aposiopetic
- aposporic
- aposporous
- apospory
- apostasy
- apostate
- apostatize
- a posteriori
- apostle
- apostlehood
- "Apostle of the English."
- Apostles' Creed
- apostleship
- apostolate
- apostolic
- apostolical
- apostolically
- apostolic delegate
- Apostolic Father
- apostolicity
- apostrophe