This word is acceptable for play in the UK dictionary that is being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. An instrument, with a handle and a flat part covered with parchment or crossed with catgut, used to strike a shuttlecock in play; also, the play of battledoor and shuttlecock.

n. A child's hornbook.

"In our Art they have many shadows, or rather I should say, reflections; which are more or less distinct according to their proximity to the living originals, and, like the images in opposite mirrors, becoming themselves reflected and re-reflected with a kind of battledoor alternation, grow dimmer and dimmer till they vanish from mere distance."

battledore