An environment was the natural and/or man-made surroundings in which one lived and worked. Environments could be described in terms of physical or intangible characteristics.
In 2364, after listening to Geordi La Forge's joke, Data clarified, "So the difficulty in attaining such complex positioning in zero gravity environment, coupled with the adverse effect it would have on the psychological well-being of the average Human male, is what makes this anecdote so amusing." (TNG: "Conspiracy")