U

hi-fi

noun

high fidelity.
a phonograph, radio, or other sound-reproducing apparatus possessing high fidelity.

adjective

of, relating to, or characteristic of such apparatus; high-fidelity.

noun informal

1. short for high fidelity
2. (as modifier)hi-fi equipment
a set of high-quality sound-reproducing equipment

adj.

1947, abbreviation of high fidelity (1934), of radio recievers, in reference to their quality of sound reproduction. Hi as an advertiser’s phonetic shortening of high is attested by 1914.