1(broadly) prose (as opposed to verse)
2(more narrowly) free-form literary prose, such as essays, sketches and reflections
Examples
zuó tiān昨天wǒ men我们xiě写le了wǒ men我们de的sǎn wén散文。
昨天我们写了我们的散文。
Yesterday we wrote our essays.
他不是诗人；他写的是散文。
He isn't a poet; he's a prose writer.
他不是诗人；他是个散文作家。
He isn't a poet; he's a prose writer.