There is only one file type that uses the .TIAPP extension:
TIAPP files are used for distributing apps for use in the TiTanium web browser. The apps are often uploaded by developers to the TiMedia App Store where they can be downloaded and installed by other TiTanium users. To install the TIAPP, simply select the app in the TiMedia App Store and it will be installed and opened in TiTanium.
NOTE: TiMedia TiTanium is discontinued.
Updated: December 27, 2018