PHRASAL VERB (在露天里）蹲守，长时间驻留 If you say that people camp out somewhere in the open air, you are emphasizing that they stay there for a long time, because they are waiting for something to happen. →see: camp 4(在露天里）蹲守，长时间驻留 [emphasis]
...reporters who had camped out in anticipation of her arrival. [VERBPREP.]