Phony scientific or technical dialog meant to sound real without any reference to reality. Common in Star Trek as the "science" is largely phony, and dialog discussing it would need have to be made from whole cloth. An example being "Free up a kilo-quad from the computer so we can reprogram the flux inverter to energize the tailoron particles".
Technobabble is itself not a bad thing except when used as a Deus ex machina to solve a plot in the last five minutes of the episode.