I've lived under the impression that the word beamer is an American slang word for a BMW vehicle and a false friend to German speakers: beamer does not mean projector.
Recently though, I heard an American¹ use the term beamer to mean projector. I asked her about it and she said that beamer can indeed mean projector in American English.
Is that true? Is it valid in American and/or British English to use beamer to refer to a projector?
I assume it would be a rather recent or localized development since Merriam-Webster does not list that meaning. Neither does the Wiktionary entry. Also painfulenglish.com's blog entry from 2013 labels the usage a "mistake".
On the other hand, both the Cambridge English Dictionary and the Macmillan Dictionary state that beamer means data projector, as Edwin Ashworth helpfully pointed out in the comments.
¹ That's how she introduced herself and she did sound like a native speaker to me.