What are Cinematic Special Effects?

Definitions of special effects on the Web:

Visual effects applied to clips and sequences such as motion effects, layering, and filters.
www.brynmawr.edu/filmstudies/writing/glossary.html

A general term for various photographic manipulations that create fictitious spatial relations in the shot, such as superimposition, matte shots, and rear projection.
www.mhhe.com/socscience/art-film/bordwell_6_filmart/student/olc/glossary.mhtml

Artistic effects added to a video production in order to enhance the production by creating drama, enhancing the mood or furthering the story. Special effects may vary from the limited addition of patterns or the mixing of several video images together, to sophisticated digital effects such as picture compression, page flipping and three-dimensional effects. Special effects are usually created using SEGs.
ide.cc/html/filmterms.html

A term used to describe special theatrical make-up effects, as well as other theatrical and film effects. Often abbreviated as SPFX or F/X.
www.monstermakers.com/glossary.html

Sound or video used in the editing process to heighten drama or suggest a time, place or story element. Often used as a transition.
www.pbs.org/weta/myjourneyhome/teachers/glossary.html

Artificial effect used to create an illusion in a movie.
www.teako170.com/glossary5.html

Awkward term often given to sound effects. "Special sound effects" is a useful description, though, for out-of-the-ordinary effects that have to be created.
www.northbeachpost.com/handy_glossary.html

Use for person(s) involved in the creation of action sequences and/or of apparent action or sound using photographic, mechanical, electric, optical, or electronic devices. Effects range from simple optical effects to elaborate explosions, miniatures, computer- produced action, sets, or props. The term also includes stunt arranging, fight arranging, flying sequences, stunt men, etc. For special sound effects, use "Sound." For animated effects, use "Animation."
www.cinema.ucla.edu/CPM%20Voyager/relatorterms.html

Special effects are tricks of sight and sound mostly achieved by combining technology, ingenuity and creativity and employed in films to facilitate suspension of audience disbelief.
www.filmschools.com/glossary.html

Special effects (abbreviated SPFX or SFX) are used in the film, television, and entertainment industry to create effects that cannot be achieved by normal means, such as depicting travel to other star systems. They are also used when creating the effect by normal means is prohibitively expensive, such as an enormous explosion. They are also used to enhance previously filmed elements, by adding, removing or enhancing objects within the scene.
en.wikipedia.org/wiki/Special_effects