Signal booster is a device used to amplify or strengthen a signal, such as an audio or radio signal. The two crossword solutions for the term signal booster are preamp (6 letters) and amp (3 letters). Preamp is short for preamplifier, which is an electronic amplifier that is used to increase the strength of a weak signal before it is sent to the main amplifier. Amp, on the other hand, is short for amplifier, which is an electronic device used to increase the strength of a signal after it has been processed by the preamplifier. Together, preamp and amp form a signal booster, which is used to boost the strength of a signal.