Definition of tiddy:
(n) :
(UK, dialect) The European wren.
(n) :
A minor river in south-east Cornwall, England, which joins the River Lynher.
(n) :
(humorous, vulgar) Alternative spelling of titty (“breast”). [(slang, vulgar) A breast.]
(adj) :
(UK, informal) Alternative form of diddy (“very small, tiny”). [(UK, informal) Very small, tiny.]