Translation

semi means "Cicada" in English.

semi is normally written with katakana, as セミ.
semi written with hiragana is せみ.
semi written with kanji is 蝉.
This word contains non-jouyou kanji 常用漢字.
Romaji se mi
Hiraganaせみ
Katakanaセミ
Kanji 蝉
School Level ✕

Further Reading

Wikipedia: セミ (Cicada)