The term implies that the plant is neither a hybrid nor a selected cultivar that is any different from the native plant, even if it is growing where it would not naturally be found.
The term can refer to the whole plant, even when not in bloom, and not just the flower.
More exact terms include: In the United Kingdom, the organization Plantlife International instituted the "County Flowers scheme" in 2002, see County flowers of the United Kingdom for which members of the public nominated and voted for a wildflower emblem for their county.
For example, Somerset has adopted the cheddar pink (Dianthus gratianopolitanus), London the rosebay willowherb (Chamerion angustifolium) and Denbighshire/Sir Ddinbych in Wales the rare limestone woundwort (Stachys alpina).
Media related to Wild flowers at Wikimedia Commons