the last major instrument to be introduced to the modern symphony orchestra; a refinement of all others that preceded it, having a conical bore, large cup mouthpiece, and low, unpiercing mellow sound, unless some of the guys from the tuba section of the marching band at the Univesity of Southern California have a blow on one (or 16). May be upright, with a recording bell (this is a "recording bass," not a "recording tuba"--it replaced string basses on early recordings), helicon, sousaphone, or a silly marching version. I have played them all!
(from the latin tuba, meaning trumpet)
The proper name for a tuba player is "tubist," which is a shortened form of "tubaist," which is considered archaic. (Ask your local professional tuba player for details.)