Cal. Pub. Resources Code § 29110
"District" means any public agency, other than a local government, formed pursuant to general law or special act for the local performance of governmental or proprietary functions within limited boundaries. "District" includes, but is not limited to, a county service area, a maintenance district or area, an improvement district or improvement zone, a mosquito abatement district, a resource conservation district, an irrigation district, a reclamation district, a sanitary or sewer district, or any other zone or area, formed for the purpose of designating an area within which either an assessment or a property tax rate will be levied to pay for a service or improvement benefiting that area or a special function will be carried out within that area.
Ca. Pub. Res. Code § 29110