思わず
おもわず · omowazu · JLPT N3 · adverb
spontaneous
😮 思わず = omowa (think) + zu (without): done without thinking
思う (omou) means to think; the old negative ending -zu turns it into without thinking. So 思わず describes something you do before your mind catches up, like laughing or blurting out a word on reflex.