1540s, from Middle French parallèle (16c.) and directly from Latin parallelus, from Greek parallelos "parallel," from para allelois "beside one another," from para- "beside" (see para- (1)) + allelois "each other," from allos "other" (see alias). As a noun from 1550s. Parallel bars as gymnastics apparatus are recorded from 1868.
Adjective Of or relating to lines or surfaces that are separated everywhere from each other by the same distance.
Noun Any of the imaginary lines encircling the Earth's surface parallel to the plane of the equator, used to represent degrees of latitude. See illustration at longitude.