(UK, slang) Hard at work; preparing oneself to work hard.
2007 April 6, Gold Coast Bulletin, [http://www.gcbulletin.com.au/article/2007/04/06/4336_columnist.html "Call of Sea Sirens"]:
No comments yet — say something.
Add your own interpretation of "head down, bum up".
Regional slang from around the English-speaking world — British, Australian, Irish, Caribbean, Nigerian, Filipino, AAVE, and the hyphenated-English dialects that make the internet sound local.
See all Regional & Other slang on Slangora.