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The Japanese word

固い

is pronounced
katai | かたい
means
stubborn, firm (not viscous or easily moved), certain, solemn
Examples:
トムは頭が固い。
tomu wa atama ga katai.
Tom is stubborn.
彼らは固い握手を交わして別れた。
karera wa katai akuju o kawashi te wakare ta.
They parted with a firm handshake.
僕たちの先生って本当に頭が固いよね。
boku tachi no sensei tte hontōni atama ga katai yo ne.
Our teacher is really stubborn, isn't she?
クモの巣を作るには、このきぬの枠を作り、それを木や垣根のような固い物体に固定させることから始める。
kumonosu o tsukuru ni wa, kono kinu no waku o tsukuri, sore o ki ya kakine no yō na katai buttai ni kotei sa seru koto kara hajimeru.
To make a web, it starts by making a frame of this silk and fastening it to hard objects, such as trees or fences.
Examples sourced from tatoeba.org