plangent = having a loud reverberating sound

"Plangent" shows up at the end of Ngaio Marsh's mystery Killer Dolphin. (It's the first book featuring Peregrine Jay.) Anyway, one of the characters reports thinking of The Cherry Orchard at the time just before the murder. Later, it's revealed that a guitar string had been plucked -- and the Chekov play ends on a "single plangent note."

This is one of those words that I've read multiple times but never bothered to look up, because I could figure it out from context. But it's always good to know what words actually mean. :)