He pondered and rubbed his forehead, and, strange to say, after long musing, suddenly, as if it were spontaneously and by chance, a fantastic thought came into his head.
An accident on a staircase, spontaneous combustion of a shopkeeper from alcohol, a fire in Peski…. a fire in the Petersburg quarter…. another fire in the Petersburg quarter…. and another fire in the Petersburg quarter….
The extraordinary ferocity with which Razumihin received this "spontaneous" mirth gave the whole scene the appearance of most genuine fun and naturalness.
She had been struck at once by Raskolnikov’s poor surroundings, and now these words broke out spontaneously.
Then he got up, took leave with an impressive and affable bow, while blessings, warm gratitude, and entreaties were showered upon him, and Avdotya Romanovna spontaneously offered her hand to him.
There are no more uses of "spontaneous" in the book.
Show samples from other sources
The group broke into spontaneous laughter.
He bubbled with enthusiasms, and his faintest smile or lightest laugh seemed spontaneous and genuine.