Collins English dictionary defines this as 'the branch of astronomy concerned with the description and of the surface features of the moon'.
I came across it while encountering the stunning pastel works of master pastellist John Russell (1745 - 1806). I love the portrait of the little girl with cherries: it's her hair that says the most about how alive she is: it seems to swing with her head as she holds the cherries out to show you.
Then there is the selenographic portrait of the moon waxing gibbous. Amazing, and amazingly modern as a subject -- but more carefully rendered and studiously observed than most contemporary pictures (Russell was a serious moon-watcher). Both of these works are reproduced in the glorious book, The Art Of The Pastel, which I am making my way through with great savour.