From Longman Dictionary of Contemporary Englishspend a pennyspend a pennyBritish English spoken old-fashionedHBH to urinate – used when you want to avoid saying this directly → spend
Examples from the Corpus
spend a penny• You do not spend a penny.• Raising cash to spend a penny A CO-OPERATIVE of local councils could help reopen Langbaurgh's public toilets, a councillor claims.• My father said not to spend a penny more than I need.• Weeks she'd been badly, and he wouldn't hear of spending a penny on a doctor. 