I would call it strapped rather than bridged when combinging amps together.
Each manufacturer calls thier own system for doing this different things.
The trick is that both amps have to be exactly the same model and same settings.

http://www.pioneerelectronics.com/PUSA/Products/CarAudioVideo/Amplifiers/ChampionshipSeries/PRS-D1200SPL

Multi-Amplifier Synchronization System (MASS)
Pioneer's proprietary Multi-Amplifier Synchronization System (MASS) technology allows one amplifier (the master) to control the settings of other amplifiers when two or more amps are “strapped” together. Especially important for multi-amplified systems, this powerful Pioneer technology eliminates the need to adjust each amplifier gain separately.