(of rock) appear or be exposed at the surface of the earth
（岩石、石头）露出地面；露头
To appear unexpectedly or occasionally
意外出现，偶然出现
“one of the many theories that keep cropping up in his story”(&b{Christopher Lehmann-Haupt})
“一个在他的故事中不断意外出现的理论”(&b{克里斯托夫·莱曼——豪普特})