best friend

: superlative ofgood

:  excelling all others

:  most productive of good :  offering or producing the greatest advantage, utility, or satisfaction

: superlative ofwell

:  in the best (see ¹best) way :  to greatest advantage

:  most

:  the best (see ¹best) state or part

:  one that is best

:  the greatest degree of good or excellence

:  to get the better of :  outdo

:  had best (see ²best 1)

:  one attached to another by affection or esteem

:  acquaintance

:  one that is not hostile

:  to act as the friend of :  befriend

:  to include (someone) in a list of designated friends on a person's social networking site