You can with a macro.
{$macro on}{$define Tauto:=TSmartpointer}
This can maybe have side effects, though.
Noting PascalDragon's comment of a few days ago that "Macros are only matched on a full token.", i.e. there's no risk of a substring match.
They can be very useful indeed, particularly since (unlike C macros) they can be multi-line. It's unfortunate that they can't take parameters, but TBH I can't think of a single macro-expansion preprocessor that is neither embarrassingly primitive nor impenetrably esoteric.
MarkMLl