promiscuous
Pronunciation: /prəˈmɪskjʊəs/
adjective

Origin:
early 17th century: from Latin promiscuus 'indiscriminate', (based on miscere 'to mix') + -ous The early sense was 'consisting of elements mixed together', giving rise to 'indiscriminate' and 'undiscriminating', whence the notion of 'casual'