Definition of "tuba"

tuba¹

/ˈtjuː.bə/

noun
plural tubas
1. A large brass musical instrument, usually in the bass range, played through a vibration of the lips upon the mouthpiece and fingering of the keys.
  Quotations
  One version of the large tuba, popular in marching bands, is called a sousaphone in honor of bandsman John Philip Sousa.
  1990, Thomas D. Rossing, The Science of Sound, page 230
2. A type of Roman military trumpet, distinct from the modern tuba.
3. A large reed stop in organs.
noun
plural tubas or tubae
1. (anatomy) A tube or tubular organ.

tuba²

noun
uncountable
1. A Malayan plant whose roots are a significant source of rotenone, Derris malaccensis.

tuba³

noun
plural tubas
1. A reddish palm wine made from coconut or nipa sap.