What does bi amp able mean?

Bi-Amping is the technique in which you split a signal source with a crossover, and then each resulting signal path is amplified separately and then sent to the speaker enclosures. Most commonly used in Live Sound reinforcement and Hi-Fi monitoring systems, this allows each signal to be independently amplified for each speaker. Tri-Amping is splitting the signal into three signal paths, usually with a crossover, one signal is processed and sent to the Tweeter, another to the mid-range, and one to the woofer.