To allow things to develop naturally without intervention or restraint; to indulge someone or let them do as they please; often used in a negative sense to describe neglect or a lack of control.

a well where water flows to the surface naturally under its own pressure or due to gravity, without the need for a pump

Ziliujing District of [[自贡市|自貢市|zi4 gong4 shi4]] in Sichuan province

Irrigation of land by allowing water to flow naturally from a higher elevation to a lower one using gravity