To call forth or summon, often by sacred name in a solemn manner. To bring forth into the mind and often into the material world. To implore earnestly.
You can summon up an image of a blue sphere in your mind, or you can summon up the wind.
Note that with much in magick, there is a sense of cooperation and connectedness here. You summon an image or energy force within yourself first. This may be as straightforward as entering the complimentary mind state for your working. Next you call forth this energy from your surroundings (like attracts like, within/without, above/below) or you call it forth from within yourself.