Is the Channel shortening similar to Time domain Equalizer (TEQ)
Most likely people use different words to describe the same concept. This happens quite often. The TEQ is the more general term and also used to equalize other methods that OFDM, while CS is related to OFDM and tries to make the channel shorter so that it fits within the CP duration.

You can check online, you will find that almost all articles related to CS are in OFDM whereas the TEQ is a general term 

Good luck