Holiday, BillieHol‧i‧day, Bil‧lie /ˈhɒlədeɪ $ ˈhɑː-, ˈbɪli/(1915–59) a US jazz and blues singer, who was also called ‘Lady Day’ and is regarded as one of the greatest jazz and blues singers ever. She wrote her life story in a book called Lady Sings the Blues, which was later made into a film.