Very aggressively, vigorously, or enthusiastically. Primarily heard in UK. We've been working like billy-o all month to get this finished in time. During the economic boom, people spent money on credit like billy-oh, with no regard for how they'd pay it all back.
like billy-overy much, hard, or strongly. British informal
1995 John Banville Athena This skin tone is the effect of cigarettes, I suspect, for she is a great smoker…going at the fags like billy-o.