Словарь синонимов английского языка - extemporaneous

(adj) unstudied, unpremeditated, extempore, extemporary, impromptu, improvised, spontaneous, unrehearsed, extemporized, unprepared, unplanned, unscripted, offhand, ad lib, extempore, Colloq off the cuff: Though extraordinarily well-organized, Charlotte's speech was entirely extemporaneous.