Are Trans-Neptunian Objects (TNOs) asteroids? Are Trans-Neptunian Objects (TNOs) asteroids?

Please, base your answer. If possible, give sources. Thanks.
The IAU does not give a definition of "asteroid" (in contrast to its defintion of "planet") The definition of "asteroid" is therefore determined by actual use, rather than a specific authoritative source.

The IAU in its guidelines on "naming" doesn't use the term "asteroid" (except qualified as "near earth asteroid". The term is somewhat ambiguous.  Instead it considers "planets", "dwarf planets" and "minor planets".

Minor planets can be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, and other trans-Neptunian objects.

Initially solar system bodies were classed as "comet" (appears fuzzy due to a coma of dust and gas) "asteroid (appears star like, a single point of light with no fuzziness). The planets appear disc-like.

TNOs have no coma, but their surfaces are dominated by ices (and would start to evaporate if ever brought to the inner solar system).  Thus they are rather different from the traditional rocky asteroids.

So you should avoid using an unqualified "asteroid" as it may be ambiguous. You can say "minor planet" if you want to include both TNOs KBOs and classical asteroids.  Or "Main belt asteroid" for those between Mars and Jupiter. 

If you read "asteroid" it would normally exclude the outer solar system bodies. But as it may be ambiguous, so read the context.