IPA: /ˈtjuːbɪst/
KK: /ˈtjuːbɪst/
A person who plays the tuba, a large brass musical instrument with a deep sound.
The tubist performed beautifully at the concert last night.
Tubist → It is formed from "tuba" (from Latin, meaning trumpet or tube) and "-ist" (meaning one who practices or is concerned with). A tubist is one who plays the tuba, a brass instrument that is shaped like a tube.
Think of someone who plays a 'tube' ('tuba') instrument — that's why a tubist is a person who plays the tuba.