[spil-wey] 
| a passageway through which surplus water escapes from a reservoir, lake, or the like. |
| spill·way (spĭl'wā') n. A channel for an overflow of water, as from a reservoir. |
spillway
passage for surplus water over or around a dam when the reservoir itself is full. Spillways are particularly important safety features for earth dams, protecting the dam and its foundation from erosion. They may lead over the dam or a portion of it or along a channel around the dam or a conduit through it.
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