IPA: /ˈrɒkɪtə/
KK: /ˈrɑkɪtər/
A person who designs, builds, or launches rockets, or someone who is involved in rocketry.
The rocketer successfully launched the new model rocket into the sky.
Rocketer → It is formed from "rocket" (from Italian *rocchetta*, meaning a small bobbin or spool, which later came to refer to a projectile) and "-er" (meaning a person who). A rocketer is a person who uses or operates a rocket.
Think of someone who operates a 'rocket' — the '-er' just means a person. A rocketer is someone who works with rockets.