adverb taking the 'to' particle
Mimetic adverb describing the sound or state of teeth chattering, often from cold or fear. Used with と.
寒くて歯がガチガチと鳴った。
My teeth chattered from the cold.
Describes a person or body part frozen stiff, or rigid with nervousness. Used as a na-adjective.
緊張で体がガチガチになった。
My body went stiff from nervousness.
na-adjective, noun which may take the genitive case particle 'no'
rigid; inflexible; overly serious
Describes a personality, mindset, or attitude that is stubborn, inflexible, or excessively serious. Used as a na-adjective or no-adjective.
彼はガチガチの考え方を持っている。
He has a rigid way of thinking.
adverb, noun which may take the genitive case particle 'no'
voracious; intense; without pause
Describes doing something with relentless intensity, such as studying or working hard without a break. Used adverbially or as a no-adjective.
試験前はガチガチに勉強した。
I studied intensely before the exam.