The Collaborative International Dictionary
Rising main
Rising \Ris"ing\, n.
The act of one who, or that which, rises (in any sense).
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That which rises; a tumor; a boil.
--Lev. xiii. 10.Rising main (Waterworks), the pipe through which water from an engine is delivered to an elevated reservoir.
Wiktionary
rising main
n. The pipe through which water from an engine is delivered to an elevated reservoir.