The definition of a free spirit is someone or something who lives by their own wishes and is unconstrained by society.
An example of a free spirit is an artist who communes with nature and spends her days painting odd paintings and living the way she wants.
a person who lives according to his or her own wishes and beliefs, unconstrained by society's conventions; nonconformist
One who is not restrained, as by convention or obligation; a nonconformist.
(plural free spirits)