IPA: /ˌsɛmɪˈfaɪnəlɪst/
KK: /ˈsɛmɪˌfaɪnəlɪst/
A person who takes part in a semifinal round of a competition, where the winners advance to the final round.
She was excited to be a semifinalist in the national singing competition.
Semifinalist → It is formed from "semi-" (meaning half) and "final" (from Latin "finalis", meaning pertaining to the end or limit) and "-ist" (meaning a person who). A semifinalist is a person who reaches the half-way point in a competition leading to the final round.
Think of 'semi-' meaning half, and 'final' referring to the end — a semifinalist is someone who is halfway to the final.