Wiktionary
bumfreezer
n. (context slang English) an Eton jacket or other similar short jacket.
Usage examples of "bumfreezer".
Ah, Mackilwraith, if you could but once have seen me in a bumfreezer and a clean collar, singing "Love was once a little boy", it would have made a better man of you!
His short bumfreezer jacket was in the regiment's same distinctive 247 burgundy-red with black silk lapels.