It wasn’t originally. The term computer was used in 1617 when it first became popular. It was a human being who could use a pencil and pen to do calculations. Above are NASA’s “rocket women”, women who were responsible for computing the human part of the space program.
Modern computers can be described as electronic, rather than electrical. An electric device uses electricity to produce energy. An electric light converts electricity into light, and sometimes heat. My electric chainsaw converts electricity into mechanical motion.
These electronic devices include a computer, a radio and a TV. Fundamentally, they use electricity to process information. There are some pitfalls. My electric guitar converts the vibrations of the strings into electrical impulses. My amp converts those impulses into loud sound pressure waveforms. This is both an energy conversion and information processing process.
With this guitar, its unambiguous, as the sound is optionally picked up by per-string piezoelectric transducers and run into a digital signal processor — a computer optimized for processing audio signals. This lets it emulate the sound of various other guitars. So this is absolutely an electronic guitar, though you really don’t hear that said very often.