INFORMAL

adj. 1 unceremonious, casual, natural, unstilted, familiar, ordinary, everyday, unaffected, unassuming, unpretentious, simple, relaxed, free, free and easy, Brit common or garden, US garden-variety We had an informal dinner in the kitchen 2 unofficial, unconventional, unconstrained, casual, everyday, simple On duty he wore informal clothes - blue jeans and a denim jacket 3 vernacular, colloquial, simple, unaffected, ordinary, unpretentious, everyday He uses informal language devoid of scientific jargon