(n) A person's best clothing, especially the clothes one reserves to wear to church on Sunday.
(n) top outfit you've got that will be worn to church on Sunday
Sunday best in Community Dictionary
noun "Sunday most useful" defines the clothes some wear to church on Sunday. They are called "best" simply because they're allowed to be your nice / dressy clothing. by Bernadette HummerReport definition
the most effective musical organization on long island.Maybe even globe in like 2 yearsIm not joking.http://www.myspace.com/sundaybestofficial by Mariah HornakReport definition
the best intercourse on sunday morningafter a long ass week-end of fucking partying. by Abbie KoepkeReport definition